I have an FE and it's a fine camera capable of accepting a massive range of some of the finest lenses ever produced. I've also owned OM1n, OM2n, OM2SP and OM4 cameras down the years and, although the range of lenses available doesn't match Nikon, the quality does - if you can find them. I'm not suggesting OM Zuiko lenses are scarce, per se, but they are nowhere near as abundant as Nikkors.
Functionality is much of a muchness, IMO. Both have great ergonomics and I've found both to be extremely robust and reliable. The OM will probably chew batteries faster than the Nikon.
If you can, try both. If you get to shoot with both, using equivalent lenses, I'll be you won't be able to tell which camera took which photo. My advice is to go with the one in best condition which suits your hand and your pocket.