I have a 2011 Yamaha SX210, which is a twin engine 21 footer. Really like it as an all around family boat. Ours has been 100% reliable. Literally, it has not had one problem since we bought it new. About the only thing I don't love about it is the noise level at higher speeds. It's pretty loud. Other than that, no complaints at all. It took a bit to really get comfortable with the low speed handling, but now it is second nature. Higher speed handling is very responsive but the boat is sensitive to cross winds. Addition of Cobra steering fins made a significant difference in tracking at all speeds, but for me the biggest improvement they provided was a planing speeds crossing wakes or other rollers at shallow angles.
Regarding Yamaha vs. Chaparral: Honestly, I think the overall build quality of the Chap looks better than the Yamaha. That said, the Yamaha engine/drive setup is very well-known for reliability. The Rotax setup in the Chap should be reliable as well, but the superchargers do require some periodic maintenance and the lack of cleanout ports is not something I see as a "feature" as a stick or piece of bark getting lodged in the pump will stop you in your tracks until you can clear it. Easy with the ports. Not so much without.. That brings me to another thought - these boats are really not ideal for waters with a lot of surface debris. Not an issue for us, since the lakes on which we boat are quite clean.
Oh, yeah - I'd definitely go twin engine. Chap's 22 footer is a twin. Beautiful thing about that is that you can still get back to the dock (slowly, though) if something happens to one of your drives. The twins also accelerate hard, which is a fun characteristic!
