FWIW:
I've been flying the SV50 for a couple of years, very smooth, nice engine. But I've seen two with twisted cranks, these Chinese twins, (100cc included), have weak cranks, they don't take propstrikes well. If longevety is paramount go with a single, if smoothness and cool matter go with the twin.

The cheap Chinese engines can be a bargain, if you know engines and can work on them some. Engine guys will tell they won't last, no they won't last like a 3W or DA, but they will serve the average Joe fine. Most engines die from being stufted into the ground. Cheap Chinese engines will last easily 200 hours, that's 800 flights, how many years flying is that for you?

Go over-kill on control horns and linkages, they're cheap insurance. I like hinge points for hinges. If you get good HiTec servos, the arms that come with them are fine, you don't need $10 aluminum arms.