I have a M-6 and had a MXT when they first came out, I now wish that I would have kept it.
The MXT has a different rod, I like that grip better than the "S" rod, some like the "S" rod better.
The MXT has a Threashold tone in the disc mode and the M-6 is Silent Search in the Disc mode.
The MXT is single tone in the Coin mode and the M-6 is a single tone with the trigger in the center and with the trigger pushed forward, it then has 7 tone's,,2 of the tone's are in iron.
Some like to hunt coin's in the Relic mode of the MXT.
Both use the same coils.
I am a coin hunter and the place's that I hunt, I use the M-6 with the Disc at zero or 9 o'clock and Tone ID on.
The small coil is a must, I use the 5.3 and some like the small DD 4x6 coil.
I also have the 6 x 10 DD coil for other places.
I made some good finds with my M-6 in a very trashy place that had been hunted by others with other units. The pic is one day at that site.
You can't go wrong with either one.
Good luck & HH.
BJ