I have a Motion Pro twist throttle on every quad in my garage, I feel they are a quality product. I had one break, but that was because the quad flipped at speed and landed upside down on the bars, can't blame the throttle itself for that one.
Using a twist is very rider specific, if you have never used one on a quad, I wouldn't recomend one. Like crwh45, I have always ridden dirtbikes, so a twist is natural to me. If I had to ride with a thumb throttle, I would quit riding, that is how much I hate them.
Doug