If so, we hope you will register now and join our community! I personally prefer a 421 on guitar, but the sm7 is more of an all-around useful mic. SM57 + Sennheiser MD 421 mic placement; Are you a heavy metal guitar player, collector or enthusiast? Hey all, did some search and got some good info but I'm particularly interested in opinions regarding using the MD421 or PR30 paired up and mixed with the SM57. Most will say the SM57 is their “go to” mic, but I think this little microphone shootout might make you rethink that. As for sm7 vs 421, as mentioned, the 421 is gonna give you more "bite", the sm7 is thicker sounding. Registration is free and easy. If guitars are your priority, though, try to check out the R92. Over the last few months I’ve had several recording engineer buddies (that know WAY more about recording drums than I do) recommend trying a Sennheiser 421 on my snare drum.