I have owned a HRX217HYA since July 2012, and pretty much use it commercially. Not tons now but 25+ lawns a week in the summer. I have not had a single problem with the transmission, and the blade brake clutch is a good feature to have. You don't have to use the speed control lever to change speeds, you can just depress the bar less and it will slow down, also. I have never used a HRX217VKA out of the dealer, but for me I would think the paddles would get my hands tired. You don't need to use your thumbs, you can use your palms, so I guess that is a little better. If you don't need the extra features, more powerful engine, and are OK with the Smart Drive, then the HRR216VKA might be good enough. This year it does have a Clip Director, though it's different from the HRX's, so that is one good thing.
Ask if you have any more ?'s.