I am new to trials (1 year) and I've had three GG bikes in that time. In one year I have ridden hundreds of hours with lots of guys on different bikes including older bikes. The older GG JXT's are great bikes, in fact my uncles is INCREDIBLY well used and abused but still runs like a champ. It just keeps going and going and going….
My first bike was an 05 GG 300 and it to was BEAT, never babied, ridden hard by a big guy and used A LOT. Although very ugly this bike still performed flawlessly and the guy I sold it to is still riding the wheels off of it without incident. Long story short in my experience all the trials bikes are great, they all last a long time, they take an incredible beating and although brand loyalties reign there seems to be no "good choice", just "you're choice" From experience I'd just suggest buying the cleanest and newest bike you can get your hands on. Regardless of what bike you purchase you will have a great time riding it. BTW even my 2010 GG is hard to find neutral and some hunting is involved on occasion.