Agree with BK. Depends on the Model. To me the x3x series of pioneer was the pinnacle(includes the SX-1010) for them. As for Sansui, the aesthetics after the x0x0 series leaves me with a cold and fishy smelling feeling. Aesthetics and how the sound go hand in hand for me. The "all silver" look doesn't do anything for me and I tend to gravitate towards the late 60's early 70's units. Hence my Sansui 2000, 2000a, 1000A (granted the 1000A is all silver on the front BUT Tube units are different!).
I don't subscribe to the "BIGGER, MORE switches, pots, knobs,etc" front end treatment. Smaller matching knobs, and switches placed in a logical layout that is easy to learn and is consistant from model to model (for 90% of the functions). Pioneer did this better than anyone else at the time. Sansui's I own all have different switch and pot layouts, that are not immediately intuitive.
the sound differences are not subtle between the brands however (especially the earlier stuff from the late 60's to say 1975 or so. Then I find that Sansui got way brighter, more sterile sounding where the PIONEER's didn't change that much.
It's a toss up. I'll keep my SANSUI's as long as I can maintain them. And the same for my PIONEER's. But my FISHER tube gear is what i play most.
Larry