Al,
Thank you for your reply.

On rcgfusa.com, there is also one called RCGF 10cc BM. The "BM" might be a little misleading. Usually RCGF BM engines are Beam Mounts, but in this case it means Walbro-style carb. The RCGF 10cc and the RCGF 10cc BM are identical with the exception of the BM having a Walbro-style carb. There is even an upgrade kit available. I am sure the single-needle carb works just fine, but being able to adjust high and low independently makes me more comfortable buying the BM version.

The RCGF's ability to turn larger propellers than the Evolution is a good point, I hadn't noticed that. Turning a larger prop would suit my flying style better, as I usually do "bush flying" (low and slow).

Please feel free to comment. I am particularly interested in hearing from people who have seen both engines in action, but all comments are appreciated.