The 99 looks cleaner than most at that age. You won't find one that nice for less $$ in NorCal. All good deals are stanched up in hours of being posted by Dan who will flip them for a small profit. He has beat me to ever good bike to come up in the last 2 years.
I got a 96 Beta by runnig a want add. I have put a ton of hours on it in a year with no isses. The fun per $$ has been great compare to ANY other bike i have owned... so, a low use older trials bike can be a great value. But buying one that needs work can be a money pit as trials parts are expensive and some on my Beta are not even available.
As far as the 270 vs 200. At you weight both are an option. If you want to learn slow technical turns and ballance, the core skills, many will tell you the 200 is better. If you are experenced, not afraid of going big and want to learn to jump logs the 270 would be better. If you have 2-stroke experence you know how a 125cc has to be riden over a 250. Similar differences in the 270 vs 200.
2011 690 Enduro R
2013 Beta Evo
07 450 EXC