They're more or less all the same. You get out of them the amount you put in. You need to post up a complete and detailed job spec beyond "we need a website built" and you need to properly vet the candidates on any of them. In the end it's still a trial and error process finding quality prospects and it's very much a you get what you pay for scenario. I've learned that last part the hard way as have others here. Expect cheap fast and good, and you might as well burn your money. It's not going to end well in most cases.
Edit: I've yet to find a competent Indian dev team and I've tried 6 or 7 now. Never again.