For macro, ff is better, because you get the detail. But since you loose the 1.6x crop factor, you have less zoom, so you may disturb bugs, and, you technically loose magnification, since your t2i gives you a (example 100mm macro) 160mm 2.8 with minimum focusing distance of x. With ff, you'll have a 100mm zoom, and the same x focusing distance. So if you want to leave your subjects undisturbed, get either...
-Sigma 180mm 2.8 os
-canon 180mm 3.5 l macro
-rumored canon 200mm l f4 macro
If not, then these will suit much better...
-canon 100mm macro 2.8
-sigma 105mm 2.8 os macro
-canon 100mm macro 2.8 l is
-New tamron 90mm 2.8 macro vc
-sigma 50mm 2.8 macro
But even if you go 7d, then any of the ones above work.