I recently bought a V750.
After some extensive experimenting, I've decided that Silverfast is not particularly useful to me. My high-level view of the process looks like this:
I don't see any evidence that Silverfast is capable of doing anything that can't be done (for me at least) easier and faster in Photoshop. Put another way, having already invested the considerable amount of time over the last 15 or so years becoming proficient in Photoshop, I don't see any evidence that investing time learning the intricacies of Silverfast has any pay-back. Additionally, using Silverfast feels like going back to 1998 software. The user interface is primitive by modern standards.
I'm still pleased I went with the V750, if for no other reason than it includes the wet mount holder, which I am planning on trying. But other than that, as near as I can tell the internals of the V700 and the V750 are the same.
My personal conclusion is that Silverfast is of no value to me, but wet mounting may be something worth doing, so the V750 is a reasonable choice.