I never have used one but have looked closely at the Kendon. Can't take it away from Kendon they do make a nice Trailer. Nice welds & well designed. Torsion Bar is a must for a bike trailer and that is what they use. If you are buying a used one, make sure the serial number has an "AA" in it. If it does NOT have an AA in the serial number, don't pay a bunch for it.
But no matter who's trailer you buy just make sure they did not install Chinese bearings in the hubs. They are BAD even when they are NEW. Rip them out and install some real bearings (SKF / Timken) and be ready for the road. I just purchased an awesome new trailer but it had junk (china) bearings in it which I am now replacing. That is not the place to skimp.