I think it depends on the characteristic you are looking for from you motor. My experience with RAD valves are that they improve low to mid power significantly. I've never used a V-force so can't comment.
I really like what the Boysen Pro-Series reeds did to my setup, but I think the best bang for the buck is the V-Force. Buddy put one in his '91 KX250 and I couldn't believe how much it improved off the bottom. Really clean and crisp throttle response.
I put them in at the beginiong of last season and they look like new now. I don't rev to the moon and I short shift a lot so I'm sure that helps with the life.
Cool. I just don't want to put the reeds on low tension and be replacing them every month! I'm not a pro rider by any means but I do ride the dunes quite a bit so maybe it wouldn't be a wise choice?
More power, or longer reed life. That is the question.
If your in the dunes (WOT) I would probably try the high tension setting. Mototassinari claim that low tension reaps a low end boost and high tension, top end gains. I have also read (and seen photos to prove) that the life of the V-Force reeds are way superior to the RAD valve. :cool: