The M6 is basically an MXT without Relic and Prospecting modes.(Similar weight) Now that the 6T has a smaller coil available,that would be a good/light machine with that important option. She could still do well with coins and jewelry plus it auto-tracks ground (so she could join in with you while doing saltwater beach or changing ground conditions). Weight is one thing that Whites still treats as secondary (a bit) in it's top machines,and for some,can be an issue. ( For most, there isn't one as they are still real light to them.) Was talking to a Whites guy (a few years back) and he said people still really liked the metal housing and ease of there 8 AA battery pack assembly so well that It'd most likely be used for a while. Using a plastic housing would be probably be a less expensive way of manufacturing but...they did have the system down for bending, finishing and assembling the aluminum (aircraft grade) with an added bonus of low return rate for breakage etc...so..."we'll probably be sticking with it for a while".
It turned out to be a good decision. (The machines do stay out in the field and don't come back to them much...still.)
The 6T is a departure in that the electronics are up in the control pod,and the popular 8 cell battery pack is down in the high impact resistant housing.(Imagine that would only be an easy/affordable swap out should a need arise.) That's good design. With the "juice" and the ground tracking, the 6T is a Prism in name only as I checked one out awhile back, and it definitely had a real performance increase over the other Prism models. Plus...made in Oregon. Good stuff all.