It may sound like an easy way out, but most true musicians (notice I said true musicians) know where and how to mic their
instrument for the sound that they are wanting to get. You could have what you think is the best way, and come to find out it is not. Many even carry their own microphones. I just did a show for Glen Phillips (you may remember him from Toad the Wet Sprocket if you are over 25 years old) and he brought in a $1000+ mic. It was warm and sweet and really made his voice sound great. (He was really cool and asked if we minded that he used it, very professional and great to work with).
Side note: There are those, however, who think they know what is best, but are WRONG. I had a small time opening act that said they had their own mic's. Not a big deal, I have had lots of people bring their own. When they opened their
backpack with the mic's rattling around in the bottom, I realized that they had no idea what they were doing. They had a nice collection of old
Peavey's, Nady's, Realistic (and other radio shack mic's), and one
shure SM-57. I was happy to see the 57, until I realized that they used it to mic the kick drum and usually just layed it inside the drum.