Re: Shure SM57 vs Sennheiser e609
a studio engineer buddy of mine did an A/B test on these two mics using the same amp and guitar. they sound surprisingly similar, but the 609 is a tiny bit more sizzly or shrill in the high end.
like you say, the placement is much easier on the 609 since it's flat; many pros will just hang a 609 by the mic cable in front of their speaker grille. the 609 is more expensive than a 57, if that's a concern, and it's much harder to find a 609 used. i think the bottom line is you can get the same type of raspy guitar tone that sits great in a rock mix with either one.