The keys on the VA76 are longer and a bit lighter than the SD1. They are both semi-weighted, but of the two - I prefer the Ketron action. I like the smaller key length .... it's closer to normal. (the VA76 has looooong keys, like the G1000)
Sounds are about equal with the SD1 having more prossessing on the solo sounds. There ais more "built in" vibrato on the Sd1. That could be a deterent for some players, but both have top notch sounds. The VA76 has MANY, MANY more sounds, but alot of them are only slightly different from each other.
Both units sound fantastic - it's going to come down to taste and feel.