hay mate. well the company is the same. you see thumpstar had a name change due to the easy confusion alot of people were having about the other china bikes (namely being the thumbstar, thumper etc etc...) thus they changed the name.
realistically it will depend on what thumpstar or terra moto your going to be looking at purchasing which will depict what one is better. the terra moto krusha is allright, strong 125cc motor, decent frame and suspension and goes quite well to my understanding but of course i personally think the new plastics were a big mistake and has made the bike much less attractive. of course the 06 thumpstar is a mean bike, this has been known for a long time and it doesnt really matter which one you choose in the range (superhunge 10, pro125, hunge25 expert etc...) there all pretty solid.
all in all i dont think you could go wrong with either bike, they both have a reputation to uphold and a bike which is top quality. choose any and you wont be sorry.
Cheers, Tony.