I have never used an OM system, but there is a large side aspect to your question.

If you go with Canon and Nikon bodies, specifically the autofocus models, you can use today's lenses with them.

This is not so unimportant as it may sound.

Today's lenses are OBJECTIVELY and PUBLICLY analyzed to DEATH, so all of your questions are answered and you can make objective comparisons.

So for example, the Nikon 35mm f/1.4 has only slightly more resolution than the 2.0, in the center of the image, but much more on the sides:

http://www.photozone.de/nikon_ff/596...3514ff?start=1
http://www.photozone.de/nikon_ff/444..._20_ff?start=1

but this is only important for digital sensors, not film - so yes, the $1300 difference is not justified, and yes, the Canon 35 mm f/2.0 is inferior:

http://www.photozone.de/canon_eos_ff...5_2_5d?start=1

(Canon or Nikon don't make a difference here - you can get an autofocus body from either brand for $50).

Old lenses - ask, guess, try, maybe, let me develop a couple hundred test rolls...