Steve Levine , Jul 26, 2008; 07:16 a.m.
You will get a fraction of a stop more speed, and slightly less DoF wide open with the F3.5. Both lenses are well made and are capable of professional results. I've used the "C" version of the F3.5 for years with outstanding results. The "N" versions of these lenses are newer than the "C" glass, and have supposedly better coatings.
Having used both N & C glass both indoors and out. I have never seen much difference. (of course I always use maximum shading with a bellows type lens hood.)