I bought a 633 because the deal was too good to pass on. Ran like crap out of the gate because it was way too rich on the high side. I've leaned it out and run a few tanks of fuel in it and so far, so good. Just mounted a new bar on it because I didn't care for the small nose that was on the factory bar. Haven't run it with the .050 3/8 LP chain yet but I'm sure it will pull it well enough.
It's NOT a 200T, but nothing but a 200T is....
For the little use I have for a top handle saw, I've been pleased but I'm not using it to earn a living.
The 637 should have a good bit more kick that the 633, but if you have to pay retail for one, might as well get a 192T because of the better dealer support.