What will you be using for a guidescope? Imaging with a 40D at the long focal length of the VC200 is going to be pushing it for either of these mounts. Are you planning to focal reduce it?
As a portable mount the GM8 is still pretty weighty, but at least it will still be stable enough
. I use my 8 with Orion ED80. a small 420mm refractor for a guidescope and my DSLR. Great little setup. Are you thinking Gemini controller or just the Digital Drive?
Can't comment on the SXD