the UB MTR is not just compiled as a UB, but it also has a lot of improvements that will rip newer DVDs that have various copy-protection measures on them...
now, the problem with this update is that the developer is only allowing people to test the new versions if they make a donation...that in itself is not so bad. but if the finished app is to be free (as it's purported to be), why would the developer ever want to release it if people are giving him all these donations?
i'm not criticizing him...i would probably do the same. but don't hold your breath for a UB version anytime soon. IMHO, people will donate if they feel it is useful...the handbrake developer and the isquint developer both seem to get donations if/when they need new hardware for development...