I recently traded my 70 for a f75. In my opinion it is a chattering piece of crap. I guess if you spent a year perfecting it it may be better I don't know. But I love an xterra I have done very well with it in the past so I have no plans of upgrading. My friends use a f75 ltd and a whites v3i and we all do about the same but I don't dig as many holes because I know my machine and they're machines are so complex they are still on the learning curve. Let them learn im gonna clean up!
I'm still a bit curious about 2 detectors though. The Garrett AT Pro and the Whites V3i. As I've already got 3 detectors, I'm not going to buy anymore for a while though. The X-Terra, Explorer and GTI are plenty for me.