I prefer the SM57...
the SM58 on Bass drums is used to take the "kick" sound, in combination with another cardioid condenser, far away, taking the low end. This is a good combination on bass drums but it's much better with surface pickups directly on the drumhead.
Not sure if you are referring to the screen physically blocking frequencies, or if the average singer singing with his lips on the mic (yuck) gets a slighty difference response due to a proximity effect difference of 3/4". But I would imagine it has little to nothing to do with it, they seem to be engineered to sound different.
Maybe once the foam gets filled up with spit they sound less dry...