Actually I have tuned 6 different systems: AEM, Big Stuff, Holley, FAST, Motec, and HP Tuners. Its one of the reasons I have set aside 1/2 day to just answer questions.

Of that group, I have decided to specialize on Holley and FAST for what I feel are good reasons. But an "honest" answer to your question will still sound PC because there are really things I like about both. I'll put together a simple list of features that people want from EFI; then I'll mark, without comment, which of the two handle a particular need or feature better than the other IMO. I'll gladly make my opinions public.

Remember, that in the world of electronics things change quickly, so what's hot today might be the result of the latest technical approach where one product has simply leapfrogged the other. Quality products come from competition.