Thought for years I'd take a longer boat (Z, Grind, etc.) but I took a G-Force and would not have changed if I could. A lot of folks stress comfort, but remember you can always jump on a raft anytime you want to. I've hear some folks never paddle the flats, but that seems stupid to me. On the flats hull speed is not an issue with a short boat because the river is moving and you are still faster than an oar rig.
As for surfing, I did not find it to be a problem getting on a wave. Indeed, there were several large waves that we surfed. I don't recall any that I missed b/c of hull speed (but there probably were). I did play a lot of waves and holes that would have been little fun in a larger boat and not worthwhile in a boat like a Rip. One of our oarsmen also brought his Inazone and he did have it easier getting on the waves we parked for, but by and large, I am glad I took a small boat. By way of reference, our levels were 10-15K. If for some reason you get real water (20K+) then a longer boat might well be the surfer of choice. Another advantage is that you can run the meat and melt through big stuff if you are in a spud. You can also get nice air just wavewheeling in some of the wave trains like in Hermit. I found the G-Force plenty fast when we went into Sockdolager at unawares - lots of holes to dodge and while it was no slalom boat, I had no problem moving around where I wanted in a 6"3" boat.
I think the S8 is a great boat and would be money in the Grand. It would rule the eddylines for sure. Bottom line: I'd take a shorter, more playful boat, but if you offered me a Mirage and a permit, I'd still jump with a smile on my face. The boating is really only about 1/3 to 1/2 of the experience in there. Enjoy.
Join up, suckas.
"People demand freedom of speech to make up for the freedom of thought which they avoid."
- Soren Kierkegaard