Submitted by two agencies??

there is a position at a hospital that i was submitted for today through a certain agency. After I was submitted by that agency another agency contacted me saying they could submit me to the same hospital and they are offering better pay and a bigger housing stipend for the same exact position.

Now should I go back to the first agency and tell me them so and so agency is offering more and can they match it? Or will this agency realize they have the upperhand since they already submitted me and the second agency cant submit me to the same hospital. The difference is kind of significant. the other company is giving me a car stipend of 500 tax free per month as well as a higher housing stipend by 250 more per month.

I did mention to the first agency the stipend was too low but she said she is going to send be some type of comparison chart on monday to show me how it is a good deal.

ANYYY suggestions on what to do please???