I have used a variety of 35mm and medium format cameras for SP. But for candids I prefer something small. I have used, with good success, a Canon rangefinder, a Canon QL-17, a Canon ML35 (Super Sure Shot), a Canon FTb and a Canon F-1, a Leica M3, a Nikon F2, an Oly Trip 35, an Oly XA, a Pentax KX, a couple different TLRs -- Rolleiflex and Yashica Mat -- and a Zeiss Super Ikonta B.
If I had to choose from the above for candids, I think I'd prefer either the Oly Trip 35 or the Oly XA. Light, compact, easy to use, and excellent results.