They are all very much the same
Most of the recruiters have not a 100% watertight contract with the employers.
Thet are mostly on fishing trips, to show the employer that they and only they have a selection of suitable crew available.
Very few recruiters are actually empowered to "recruit", in general a recruiter has to show that they are on the ball, and thats why they are fishing.
The reason for the what will you work for is that only the lowest quote will get the work, and thus the commission.