Howdy Jared. I have no experience with the 35 but spent yesterday tooling around on a GX50 and she just broke in and new top speed is 37.4 MPH. Not that I am in to speed but it was nice not to slow traffic on the road I was on or be passed. (Hate when they pass you on the left and then turn right) The engine is a joy to ride. Very smooth and just broke in, 1 gallon of gas lasted 100 miles. I expect much better. Great hill climber. On the engine I really can't say anything bad or enough good. The reason I have been considering the 35 or even 25 is just size. If you do get one please report.
I did a thread on the GX50 from the beginning if your interested.
New Honda 50 Some good info. Houghmade posted really great stuff as did others on the throttle which I think would be pertinent to either one you go with, but dunno that for sure.