Beta has the refinement down to a T on all of there bikes. From jetting, squash, suspension, handling, to build quality. Only sold a 300 RR never rode one but the owner has gotten many comments about the jetting being near perfect and carb and jetting are stock. Beta puts time in to develop the full product, the 4strokes have intake velocity stacks to tune intake tract length as just one example as to why they jet so well ( on the 4stroke side anway). I have never felt a need on my 2011 to have the close cartrige forks or aftermarket shock, since the stock base settings are great and revalving made them dynamite. Beta leaves very litstle that didn't get some thought.
Don't get me wrong Gas Gas bike probably turn a bit quicker, I wouldn't call it better! I still rate my 2010 300 Gasser very high. I think it just left a lot on the table, jetting, suspension, etc.
If you have one I noticed some guys talking about stability issues and softening the rear. Watch going to soft in rear, on the 4 stroke side anyway, the stock spring rate is a big contributor to head shake. Stepping up to a stiffer rear spring helps a ton. The shock will blow through its travel/chopper a bit and cause a loss of stability. Going to a stiffer rear spring solves this problem if you are using the stock springs. Generally the Beta spring calculator is good but I always error on the rear a step ahead of the scale or recommended front. Valving is good and will handle increase spring stiffness well, just soft spring rate.
Cheers,
Rick