I prefer the contract-to-hire model, but I say this as an employee. It's hard to know whether I'll like a place, but if the place is open to 3-6 month contracts, I can find out and can make it work. Unfortunately, this isn't the way things seem to work.

Also, the duration of 6 month is short enough that, even if I don't like the place, the incentive is there to put the best foot forward to get the best recommendation possible to go somewhere else.