Charlie,
Seeing as you're in PA, I'm assuming that you are talking about MAVT for vintage trials. The great thing about MAVT is that your bike doesn't have to fit into the AHRMA mold. So all the twinshock, aircooled, drum braked bikes of the 80's are still legal in MAVT.
As for the best, well, if you ask 5 vintage guys what's the best, you'll probably get 5 different answers. I've personally got an 82 SWM 240 TL and a 76 TY 175. Both bikes are great, but the SWM has a much nicer motor.
Some people love the Fantics, some love the SWMs. If you want AHRMA legal, the TY 175 is a great bike, much lighter than the 250's. My 175 weighs about 190 ready to go, and it pulls my 200+ lb butt around the sections just fine.
Basically, I'd say get what you think you want. They're all fine bikes for vintage trials. If you want to try some out, come out to White Rose on May 1 and I'm sure there will be plenty of bikes for sale, and you can probably get a demo or two.
For info on MAVT, go to www.mavt.org.
Hope this helps
Rob