James Gifford will himself tell you to choose the 5.75" over the 4" (at least he did me on the Tesoro forum). It gets better depth and the coil just works better in disc mode (his words) because of the short antenna distances of the 4". He told me for the amount of trashy areas I encountered, I might want to consider the Compadre option, and I did. A few more bucks, but it is definitely a hot detector if you don't rely on TID, with a 5.75" factory wired coil and a unit tuned to it specifically. Plus a good "on the go" unit to boot.
Cheers
Dan