Almost all of my time is in a C-150. I took a demo ride in "red" last year and the differences I noticed were:
1) The view was incredible. I was worried about how much of the ground I wouldn't be seeing, but with the seat so close to the leading edge, I was able to see what was below the plane almost to the point of what we were directly over. Visibility over the nose is significantly better because of the engine size and location. I think I left a fingerprint or two on the canopy pointing out traffic, since it felt like it wasn't even there.
2) The controls felt lighter, especially the ailerons. I didn't find this better or worse, just different.
3) Climb performance was dramatically better in the RV-12 with two people, than flying alone in the C-150. Speed picked up quickly once we leveled off.
4) Engine RPM is a lot higher in the RV-12. It was probably a little louder. I realized I would have to adjust my "listening" to get a feel for RPM by sound when watching for traffic. Again, more different than better or worse.
The air was smooth the morning I went up, so I can't vouch for how different the plane would feel on a bumpy day. My guess would be somewhere between a C-150 and C-172.
I would highly recommend finding a demo ride.
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