While I don't own either of the Radiocraft's you mention, I have flown various 35%, 40%, and 42% aerobatic airplanes. From that experience, I can say that typically the larger airplanes fly smoother and present better in the larger sizes. If one is going to compete, the subtle differences can mean a slightly better score, although probably not contest breaking if both pilots are up to snuff.

While I do think the 40% airplanes fly better, I think the reall issue becomes supporting the size difference. Cost of the airplanes. the need for a trailer for the larger ones. Does it fit in the shop well, or is it a hassle to get it in and out. How much does it limit where you can fly it, Etc. These are the issues that should be addressed first.

If you get through those, and you still can't make up your mind, just bite the bullet and get the 40%. You'll never keep looking over your shoulder wondering if you made the right decision