People will tell you there is much difference between 75 and 90 - for some reason for me it doesn't matter.
I am assuming you talk RF, i.e. M, LTM or Nikon RF mount. I were you, I'd pick anything from 75, 80, 85 and 90 (I have lenses in all those lengths) that fits your budget and your camera framelines. For example, an M2 is easier to use with 85 or 90, while M6 and up work well with 75mm. If you have a bessa R3*, it is ideal for 75mm; and so on. You can check for lens signature in the many samples that you find on flickr, have a look at the M-mount forum in my signature, for instance.
Personally, my favorite is the 75/1.4, followed by the 90/2 Summicron v3, and Nikkor 85/2 LTM. The two Leica lenses have almost identical finger print, but the 75 is obviously faster and larger.
Maybe f2 is too fast. If you want something smaller, I recommend the 90/2.8 M-Hexanon, or the CV Heliar 75/2.5. Best value for the dollar.
I haven't tried the new CV 75/1.8. Seems to be a great affordable lens as well.
Roland.