Fattys make more power than T5's through most of the RPM range except on top where the T-5's make a couple extra HP.
T5 and Fattys both do well with porting, but like you said not as much as a drag pipe.
I also feel T5 have a better finish, and cooler looking silencers as well, but the new fattys that are real chrome look pretty good too.
Or you could always buy a used set cheap off someone who is selling some like me.
Both are great all around pipes, The two choices you listed are very comparable with each other performance wise.