GT500 or GT550

[H2RICK]

As a long-time 550 owner, I can attest to the smoothness of the 3 cylinder setup compared to the 500's two cylinders. However......the 550 is in my experience quite a thirsty brute, especially around town....and with its smallish tank (intended for the 380), it is pretty "short in the legs" on any kind of a trip. 90 miles or so at highway speeds with the stock gearing and you're on reserve......and that reserve gets mighty small mighty quick. If you're not doing road trips though, this won't be a problem.
It's been quite awhile since I threw a leg over a 500 but, IIRC, they're somewhat more stable at speed because of their slightly longer wheelbase. They are also somewhat lighter.
The 550, OTOH, is a little skittish at higher speeds (80+ MPH) even if it does weigh in at a porky 440 pounds dry.....but that weight, at least, is down low so it's a pretty good cornering bike.....until the weight starts working on the suspension and you drag a pipe or the centrestand.
This is NOT a bike you'd want to do distance on IMO....unless you're under 40.
At the end of all this blather, I'm not about to trade my 550 (with all its drawbacks) in on a 500 anytime soon.
Whatever you choose, I hope it works out for you, JM.

[Craig380]

Good luck with the bike, I personally love the feel of the triples, they're a little bit magical when they're dialled in right.

It's a while since I last rode one but the 500 twin is also a really nice ride and (in some ways) quite unlike other 2-strokes with its grunt and the way it goes.

You could always buy both

[rbond]

That is a great idea, GET BOTH!!!!