I have an M6 and it's a fantastic machine, so it's something to consider as well. The other thing to keep in mind about White's, if you get an M6 or one of the MXT/MXT Pro twins, and you start to get different coils to detect in different regimes, say a smaller coil for trashy park and tot lots, a larger coil for relic hunting in the open fields and woods, you can bring your coils with you if you upgrade to a DFX or the Spectra series, the V3i and VX3.
The other thing is, because of the coil compatibility from the midrange M6 to the top of the line V3i, there are aftermarket coils available, they know that when they make a coil, they're making it for a larger set of detectors instead of just one detector alone. That's not to discount the factory which has a wide selection of coils ranging from 4x6" elliptical up to a 15" for deep work and quite a few in between.
Another nice thing about White's is the parts availability. If you start to get interest in other coils, you'll notice that the lower fiber rods and hardware kits are readily available, you don't have to Google yourself crazy trying to find parts.
Another nice thing about the White's machines which you can't tell from brochures or pictures is how well balanced they are. I think partly because they've separated the logic board/battery into the sheet metal box (which is nice to protect the electronics) and the display onto the handle. You can tell the engineers tested them in field, they've thought about the placement of the box and display to make it easy on you. Another really nice thing is the tones the machine makes, you can listen to them for hours and it never gets tiring. I'm a guitar player and some tones that some machines make annoy me, not the White's, it's got a pleasing tone that you can detect with for hours on end. It seems to be all White's machines too, I have a GMT which is equally pleasing to detect with.
Anyway, best of luck with your search for the perfect detector for you.