Over the years I've tried the F70, F75, AT Pro, and White's MXT. I keep coming back to my X-terra 70 because of how balanced and reasonably light it is with the straight shaft, gets pretty decent depth and is really flexible. I suppose if I had found more productive relic sites I would have been tempted to get another, higher-end machine to be sure I was getting all I could get, but I'm not convinced that I would be getting any significant improvement in depth. I would still have the MXT as it was the equal to the X-terra, but the thing was tearing up my shoulder.