I also use vinyl gloves. Honestly I prefer them to latex. I do massage work and vinyl is less slippery/stretchy and they usually come without powder inside (wheras one has to seek out powderless latex gloves). Those can also be cut up to create dental dams. And yes, they are just as effective. In some ways they're more effective as they don't degrade with most oils (as latex can).

Nitrile is a "cheaper" version of vinyl that can also be used, as can polyurethane as you mentioned.