The best tuner is personal preference. I like BBR, alot of people like Bama and alot of people like Jon Lund (Evo, Lethal) tunes. Just go with who ever has the best customer service and is willing to help you and has good prices lol. Bama does have that tunes for life deal.
All the tunes should be within a few HP of one another all the way through the curve. It comes down to choice. A lot of people do the Bama since American Muscle aka ChrisRose is all over the mustang forums on every site and they offer free retunes for all boltons. Pretty good deal IMO.