I ended up going with the Kipp handle version, having used an MK-V gimbal grip in the past, which also used a Kipp handle. The $422 I saved seemed like a good deal. However, unlike the old MK-V grip, the handle on the PRO grip extends out quite a bit from the gimbal handle. I didn't see this as being an issue until I got it, held it in my hands, and started bumping into it while trying to operate.
I did come up with a bit of a solution though - the clamp used on the PRO gimbal is the exact same as the clamp used on the PRO post, and since my PRO post had the silver clamp lever on it, I just swapped the Kipp Handle to the post clamp, and the silver lever to the gimbal. I feel like it's a big upgrade, and I like the way it feels in my hands much more. The Kipp handle sticking out down on the post clamp is then much more out of the way than on the gimbal.
So - just a warning for anybody who's going into purchasing a PRO gimbal sight unseen - the Kipp Handle really is a compromise, and the $422 you pay for the silver lever clamp is well worth it for having an easier to work with gimbal. Had I held both versions in my hand, I think I would have gone with the clamp lever from the start. However, if you've got the Kipp handle version, swapping it to your post extension clamp (if you've got a PRO II post) does seem to be a workable solution.
All in all, the new PRO grips are fantastic, and amazingly well made, but I thought I might save someone else the "Oh crap... what do I do now?" moment I had.