I haven't used enough SLRs to say which is the best, but of the three dozen or so I've used, the one that stands out for me is the Contax RTS. I'd only gone into the shop to have a play, nothing else, but as soon as I put it to my eye, I knew that I was leaving with it. You can almost hear the pop as the image passes in and out of focus. That big and sublime Planar f/1.4 helps a lot, too.