All dogs have health issues some where in the ped lets say your talking about well bred dogs not just BYB's. APBT's lifespan is about 12-15 years in my experience and in my kennel. If you lose them early, cancer is to blame most of the time. Health issues can be from hearts, hips, elbows, and there are a few eye disorders some lines carry. If I am missing one guys feel free to chime in.
AMbullies I can not give a lot of info on since I do not know any but I do know they can have a lot of health issues depending on where you get them from. Muggle stone AMbullies for example are known to drop dead of heart issues from bad breeding. You have structure issues with some, hearts is another big one. With the fad breeding that went on many did not pay any attention to proper breeding and you ended up with a lot of health issues. Now that the standard has been made there are good breeders trying to fix that. You just have to find a good kennel. Lifespan as with any bigger dog will not be as long but my guess would be around 10 at least.