To a degree the answer depends on the dough formulation and the crust thickness and bake time, but, in general, if the dough formulation contains little or no sugar, like a basic NY style, I would use the stone. If there is a fair amount of sugar in the dough, say, several percent (by weight of flour), or some other ingredient high in natural sugar, I would use the screen because the stone is likely to cause premature bottom crust browning or even blackening before the rest of the pizza has finished baking
You might also use a combination of screen and stone. The screen, with the dressed pizza on it, can be put directly on the stone and yanked from the oven toward the end of the bake. Or you can start the pizza on the stone and slide a pizza screen under it part way through the bake before the bottom of the crust gets too dark. In both cases, the screen lifts the pizza off of the stone surface and reduces the bottom crust coloration.