I've been using various Betas on trails for years. This is because there aren't many people in my area to ride trials with. I've done lots of trails with no seat (before Beta offered a seat) and gas bottles in my pack. Just this year I bought an Evo with a seat for the extra fuel capacity.
Most of the time a trials bike makes everything much easier. The only times I've been at a disadvantage with a trials bike is on big loose hill climbs and sand. However, the knowledge that I don't have to wrestle a 300 lb monster when I don't make a hill climb is priceless.
For trail rides I would buy an Evo 250 with a seat, trials tire, and higher gearing.