D5100 vs OM-D ??

I chose the 16-85 because I like the extra wide angle (24 mm) and the 12-50 on the OM-D is 24 mm as well (35 mm eq).

But even with the more expensive lens on the D5100, the OM-D is still more expensive, so you have to decide if the smaller size and weather sealing is worth the extra cost.