I had them both. I'll give it a shot.
Sounds:
Piano - both are EXCELLENT
Electric Piano - edge to VA7
Solo winds - edge to SD1, but both are great
Drums - tough one - edge to SD1(slight)
Organs - edge to SD1
Strings - edge to VA7 (Roland rules strings)

styles:
Rock - edge to SD1
Swing - edge to VA7
Latin - edge to SD1
Ballads - edge to VA7
Country - edge to SD1
Disco - edge to VA7
Ethnic/world - edge to SD1
**MORPHING - only on the VA7 (WAY cool)
**Mic & Harmonies - only on the SD1 (also cool)

These two instruments compare VERY well side by side, except in ease of use. The VA7 is still behind the pack in live operation. The combination of button pushes and touch screen presses make it more difficult to use in a live show, so the SD1 has an edge here. However - the VA7 has twice the polyphony, and great speakers !
(If you like gimmicks - there's the D-Beam too.....ho hum....)

I still have issues with the operation system on the Ketron, but the first impression sound is VERY good. If the new VA76 is available soon, I'll probably get one for my studio. I also think the SD1 is too closely related to the X1 to get overly excited about, but it sure sounds good. I'll never own another one until the o/s is completely revamped though. It needs to handle polyphony much better for me. Even the mic is subject to ployphinic "dropouts", which drove me nuts on the X1. The harmonies would have to be retriggered during long, sustained passages, using the hold pedal - the voice would just STOP short. Very abrupt. Hated that. For straight arranger or sequence play, the SD1 is probably the better choice of the 2, but if you like playing solo piano, the VA7 might have a bit of an edge. Too bad the Roland doesn't have a vocal mic input (the VARIphrase DOESN'T count), or the comparrison would not be so close!