Nate,
This is a very interesting observation as I intended to use my SP with only 35 or 50 lens, so figured that the SP would be the better choice for a good finder. I seldom use any my RF gear any more, preferring to use my Nikon F or Nikkormat FTn, only missing a rangefinder when street shooting fast and furious, but even then I have a F slung over my other shoulder. Grappling with focusing rings and aperture rings that rotate in opposing directions is causing me to not even bother with my RF's. But switching to a Nikon RF cures all that angst. I will shooting a 50mm most of the time, although I definitely want to have a 35/1.8 to use when I want.
So maybe I need to take a hard look at the S2 as well...