With IDine - is one FF program a little better than another?

Reason I ask, I have miles with AA and USAir. I could open an account with Delta (since I do live in Atlanta)... however, I really don't fly that much. At least, not currently.

I don't want to water down my miles and not be effective... but at the same time, I don't want to choose one plan when another could be more beneficial.

Thanks, in advance...

Jeff