I certainly second what Old Longhair says. I really like hunting with the LF coils and use the 15" LF Coiltek as my main coil. I switch over to the 6" LF Digger for places with a lot of trash, heavy undergrowth (a closed coil doesn't snag), tight spaces, too much RF interference, etc. I pretty much only use my 10x5" HF elliptical coil as a change of pace, or after I've already thoroughly hit an area; not a bad coil, but different.
A big coil often means small targets get overlooked, but with the Coiltek I find dimes all the time and even smaller targets like splitshot, .22 bullets, and tiny pieces of brass from disintegrated shotgun shells (an annoying amount sometimes.) And despite my Coiltek being the LF model, I'm not overly concerned about missing gold targets; it finds boatloads of lead, which should be right in the same range. The MF & HF should perform just as well, at a minimum.
The thing that takes getting used to is pinpointing with these big boys. Especially with tricky targets, you occasionally have to try different angles and methods to hone in on where the target is centered. With a smaller coil like the Digger, it's much more a breeze.