To me, concept is king. If I can't come up with a concept to justify an AT or powerset, I won't bother.
For example, my main is Martial Arts. MA is mainly kicks, so I decided his hands are malformed and useless for fighting. He relies on his legs and feet, which ties in nicely with the powerset. To round him out, he's also Super Speed and Super Jump. I carry the concept forward such that I won't use Brawl or any hand-based prestige or pool power with him, despite suffering from a gap in rotation early on.
Funny thing, I had the same character back in the early live days, and there was a post on the old forums about changing some MA attacks to punches. One of the mods or devs indicated they were thinking about it, but then I piped up in the thread about how I built my concept around that quirk of the powerset. In the end they didn't change MA. I probably didn't, but I like to think I had some influence on that decision.