Make no bones about it.  Bud Abbott had talent.  Lot's of it. 
He made his first film with Lou in 1940 days before he turned 45 (assuming he was born 2nd October 1895 - some reports indicate otherwise).  You only have to look at his performance in this one film to realise what a great straight man he was.  Lou was a comedian with a lot of energy, he needed a solid straight man to bring back to earth before he got too boisterous.  Bud was the perfect straightman for Lou.  I can't imagine anyone else in the role.
Physically he looked great too.  Tall, slender, he had the right face for it too.    His expressions were superb.  He really looked as if he were mean in real life.  It was great to see glimpses of him in real life footage in 'Abbott and Costello meet Jerry Springfield'.  He had a great serious voice too, a contrast to Lou's childish whines.
For Buck privates, their first starring film, someone decided he should wear a front piece toupee to disguise his high hair line (though he wasn't balding, he had that hairline for a long time).  I didn't realise it was a wig till I read about it (I hadn't watched 'One night in the tropics' by then).  It was obviously to make him look younger.    I didn't think he really needed it but it did suit him.  There was a quick shot of the boys in the nightclub near the start of 'tropics' and the lighting was bad and Bud did look older there than he did for the films he made during the next couple of years.  
Nevertheless, the wig stayed and it, well I don't know, it must of been a long term plan cos it receeded up until 1948 (which looked natural) when he finally took it off.   Except for 1945's Abbott and Costello in Hollywood where it looks as if he had a full head of hair. 
His performances during the early forties were outstanding.  He was absolutely superb in Hold that Ghost (as was Lou).  I really did love the way he let that smile slip in when Lou crashes in the piano during the dance sequence.  On screen he was very relaxed and intense at the same time.  Lou was cooperative in the act which made his job easier.   Off camera, he was very introverted and not many costars got to know him.   Everyone knew Lou, who was the opposite of Bud.  Bud's illnesses and and his drinking was clearly a large handicap during his life.
Was the stories of his drinking exagerated?  Can a man who was such a huge superstar like Bud really stop everything at 4.00 PM and then get plastered every day and night?   What about personal and stage appearances apart from obvious family commitments?   We know he never drove due to his illness (expect for a VERY brief shot in The Time of their lives) though Jerry Seinfeld, in his special gave us a story of Bud missing a ticket for speeding by using the gag 'I've got my shoes on but I'm not walking'.
Lou had a bad time of it (a huge understatement) in 1943 and while he was off sick, the radio audiences didn't want to hear Bud on his own so he had a lot of time off too.   They were both eager to get back to work and make more movies in 1944.  Lou had changed though, he was never the same.   Someone suggested to Lou that HIS name should go first.  Bud said he'd rather split up than let that happen and he won.    Though Lou won the right to recieve 60% of their income while Bud collected the remaining 40%, it hurt him very deeply. 
I found the chemistry from 1944 between them to be lacking a little from their earlier films.  Maybe it was just the way the films were written.  Lou totally messed up the production on 'In Society' by insisting on them adding the 'Susquehanna hat' routine.    Bud was much more passive concerning the production of their movies.   There was a scene in 1945's 'Here come the co-eds' where Bud slaps Lou.  It was reported that it made studio hands jump because it was so hard.    It occurs just after Lou lost the basketball match.  This was Bud's way of getting back at him I suppose.  He was venting his frustration.  Lou certainly was the dominating force behind the team.
Bud was a very fast talker in their routines but he was slowing down by the end of the forties.  There was a great scene in 1949's Africa Screams.  Bud wants them to go on Safari, Lou is more hesitant.  They do a really fast paced banter.  Bud says the same lines over 'You'll do as I tell you' and 'I'll have no arguements from you' while Lou is marvellous and more imaginative.
They were both incredible in their masterpiece 'Who's on first'.  Thoughs sometimes, I do get the feeling they are doing parts of the routine out of habit.  I do get a sense of repetition in their performances.  Not suprising when you realise how many times they performed it..
I would say Bud started to look old from 1947.  He voice started to change too.    Years of illness and alcohol was detrimental to his voice (and his waistline).   As a straightman, his slender looks and his voice were probably the two most important things about his performance.    Unfortunately, he lost both during the 50s.  In Time of their lives (1946) I was suprised at how young he looked - especially in his first scenes as the Doctor.  You would never guess he was approaching 51!  He looked younger than Lou - who was 10 and half years younger than him!
The front piece toupee came off for The Noose hangs high in 1948. An interesting year for their films.  A routine orientated film, followed by their most famous followed by one of their worse (certainly their most boring). 
By 1950, he was certainly aging.  The waistline was starting to get noticable.    He hardly took off his hat during the films of the fifties.  Lou also had a fascination with his hat in the 50s.  I didn't like that bowler hat he worse in the TV show but I'll cover that in Lou's analysis.  They were still top money earners for Universal by 1950.  They toured Europe and were enjoying life.
By 1951, Bud seemed to of aged overnight.  In the opening scenes in Abbott and Costello meet the invisible man (1951) especially.  They enjoyed a new success in their top TV show which they filmed in 1951.  Bud's voice grew very raspy and he grew a moustache and he looked very different.  Infact years ago, I had a friend who taped me some episodes from their TV show and he said he enjoyed them.  Not long after, he was round my house and while waiting on a phone call, I decided to show him 'Keep em flying'.  Lou made his entrance and my friend was saying 'Oh, there's Lou, he didn't change, but where's Bud?'.  I had to explain that Bud was in it already and he was the thin one wearing the hat.  He was very suprised at how different he looked.    He enjoyed the film :)
I think Bud was also losing control of Lou on screen too.  His worst screen moment, I reckon, was in Lost in Alaska.  The boys are throwing spears and things to the enemy in the snow and Lou bangs Bud with something.  Instead of slapping him and taking control straight away, Lou goes over the top and jumps on top of bud and Bud's hood goes over his face and all he could say was 'Now, where am I at?  Where am I at?'.    It was very far removed from the Bud of the early 40s.  His acting also went downhill for some reason.  I always thought he was a great actor.  I loved his performance(s) in The Time of their lives and I prefer his screen presence to Lou's in the Little giant (1946) too.  I believe Lou had a right to be jealous over him.   Lou wanted to switch places with Bud during filming of the Time of their lives but his pleas went unanswered.  During the last couple of films, his acting bacem very one dimensional.  His worst scting scene I believe was in Abbott and Costello meet the Keystone Kops' when Fred Clark faints and his wig falls off.  The way he carries his lines seemed a far cry of the confident Bud of the forties.
Bud's timing slowed down during the fifties.  They performed 'Who's on first?' in one episode of the TV show but Bud's voice wasn't as clear as the old days, nor was the routine as rapid fire as it should of been.  By 1954, he had put on a lot of weight.   His waist nearly as wide as his rotund partner.  He was also too old for the vigours of pyhsical comedy and it was obvious when he relied on a stuntman, because the stuntman came across as a lot more agile than Bud(and the stuntman was noticably slimmer too).  In their two films of 1955, Bud's character just wasn't the same.  He was pushy and it wasn't funny at all.  Lou's characters didn't really rely on him like the old days.  Before Lou needed a *friend* that's why he put up with Bud, now we don't know what they were doing together.  The chemistry was gone and they were *acting* like best friends for the films.
In 1956, they made their last film together and for once they learned the script and stuck to it.  The verbal routine they perform at the start of the picture didn't seem to work.  The timing was off.  Had Bud not lost nearly all his money to the IRS I would say it was the perfect time for him to retire and enjoy his sunset years (which were full of misery themselves).  It was a year later, while on stage that Lou realised his partner was loosing his straight-man knack and called it quits.
After Lou died in 1959, Bud teamed up with Candy Candido.  I really wish Bud had made one more film.  It would of been really interesting to see how he'd do without Lou.    Infact I enjoy all of Bud's solo scenes.  Where Lou would be too full of energy at times, Bud was very relaxed for the camera. he was a natural and a good actor.    I would of liked to of seen him to some drama and other types of roles far removed from the Abbott and Costello act.

Russell Dodd:  Sep 2000

Here, I gave Bud  a 'shave' in this pic of him on Venus.