I've played both, APA for over three years and as team captain active, and TAP for over a year and half, inactive right now.
Rules for 9 ball TAP and APA are very different, TAP being much more like US Open 9 ball rules, APA uses a points per ball system, both are handicap. Read the online rules if you want find out more.
The APA and TAP 8 ball rule are nearly identical, with the exceptions of having choice off the break in TAP if any ball goes down, and every shot is a called shot. That's really just about it.
TAP also has a rule called safe ball down, where you can call safe, pocket your own category of balls, and then turn the table over to your opponent. This is done mainly for defensive purposes.
Skill levels in my area drop one, and really should be more, that is an APA rated shooter of SL5 would enter the TAP as an SL4. Some of the TAP SL4s are WAY better than most SL5 APA shooter, but again, that's subjective, and may change in you local area.
I'm currently a SL5 in APA, SL3 in TAP for example. I've seen some SL6 APAs shooting as SL4s in TAP as as well.
In my area, the TAP shooters, overall, in general, are higher skilled players.
Also, another big difference is that in addition to having players dropping in SL in comparison to APA, TAP teams are allowed to shoot five players up to 25 team skill level points, where APA is 23. Our former APA had to keep close track of the team points, where it was never a problem with the TAP.
