For OR you don't need the extra "performance". But the weight saving is a big plus, and hence you can be faster (not necessarily). I'm sure you can still win races with NiMH batteries.
Personally I'm just fed up with NiMH. Expensive and too much hassle. Not to mention all the expensive charging and matching equipment. For instance that &%¤=}@! Spintec ICC charger...
I think I'll use a sledge hammer on it next year...
LiPo technology is inexpensive and very user friendly. And for practice and fun you get fantastic long runtimes.