I use a Garrett Ace 250. (previously tried a MP3 pro, maker unknown, didn't find metal deep enough for what I cut max) The Ace hasn't failed me yet, only use it on yard trees and an occasional suspicious looking tree other than yard. My blades cost about $400 and I charge $.05 more/bd ft for yard trees to pay for the detector time. Goes really quick to check and can detect in excess of 8" deep on a 6 P nail head. I do fret the first time I hit a porcelin insulator with no metal in it to register on the detector. So far I havn't even had to replace the first tooth but it will happen someday, my luck won't last forever..
