I've never flown either plane, but I can tell you from what I've seen about the Cap580, that it will not hover. Its control surfaces are way too small for any control while hovering. The plane is also way too heavy and doesn't have near enough wing area to be a 3D machine. The plane flies amazingly well for IMAC type flying, and is one of the smoothest planes I've ever seen. The RV-4 I've never seen fly, but I've never heard anything negative about it. If you want a scale plane to fly in a scale way and like warbirds, go to VQWarbirds.com. Great website, gorgeous planes. The OS FS70 would fit just right in one of those planes. I'll keep looking around, but that CAP is gorgeous and flies like it's on rails.

Also, how much experience do you have in flying? That will definitely change things.