The only reason to crop ears is cosmetic - There are no proven medical benefits.
No one knows how painful the procedure is - I tend to think of it along the lines of circumcision, it's not necessary, it is painful - But they won't remember it and it will cause no long-term damage/harm.
It is a personal decision, many feel it is inhumane, but that is their personal opinion, not fact. Most anti-croppers are very passionate and tend to get quite rude, but don’t let that sway your decision. It’s YOUR dog, and s/he’s not going to hate you for it (or even remember once the stitches are out, for that matter).
I have had one APBT cropped - Luna, my newest baby. It wasn't that big of a deal at all, just had to leave her 'cone' on so she couldn't scratch her stitches out, and clean them and put ointment on them every night - Neither of wich bothered her in the least.
I love her ears now, and I'm glad I did it. If I could go back, I would do it again - Depending on the individual dog, I will probably consider cropping with every APBT I ever own, because I personally like the look.
For more info, do a search on the forum on 'Cropping' - This has been discussed many times here.
Luna's the baby in the middle: