I have an AP ver2 for my hybrid EJ257/EJ205(H) swapped 2003 Impreza and it is convenient as hell when it comes to tuning, data-logging, etc... plus the E-readouts on AFR, Oil press, etc are nice too.
Not trying to tout the product as the end all be all in tuning products but it is user friendly, great customer support from COBB, and will adapt to any change you make to your car so long as you know how to use the tuning software associated with COBB's AP.
The OTS maps to my knowledge use non-specific relatively conservative tunes to get the power numbers they create. This is so that person X in WA doesn't get Det or CEL when person Y in SOCAL is perfectly fine. Or the other way around. If you pro-tune with an AP you can achieve better numbers and still retain the convenience of the AP based on your mods. However, you should not rely on the OTS maps to further cover any mods you have made beyond what the OTS map calls for. IE TBE + BOV + FMIC will not have their full potential realized with the AP stg 1 OTS map it may even make the car slower. Just my $.02
P.S. I'm a RA nublette but been in the Subaru world for some time now so if I missed the mark completely with this one /sorry in advance