I own both a D5100 and a D90. Granted, the controls are more convenient on the D90, but the only real difference I see is the clearer view screen on the D90. Commander? I used it and then switched to radio controls--my Phottix Strato II didn't cost that much and is more dependable than the line-of-sight Commander mode. So, generally, I use the D90 for studio work and the D5100 for landscape and low-light shooting.