to be honnest the only thing that makes a pitbike good is the price of the frame and its specs because anyone who races will go out and change forks, shockas and modify the engine, breaks to there application
there are some good models of pitpro's and i certainly do not regret the purchase of my pitpro SE as because it is the only bike (other than lxr's and ciniworks) that i am comfortable to stand up on
and any "good" brand that goes out and puts all the goodies on there bikes are usually not making much money because 'thats too much for a pitbike' atomiks are not the best in design (minus the fuse there a good frame imo)
and what makes a good bike? no one can tell you because usually no matter what bike you have you will have to revalve the forks, and shocker and maybe change a cam or map setting to your liking so the only person who can design the best bike for you is you really... so to speak its a hard subject to write about