I like the XLT very much. I had one for 3 years. The one nag I ended up with was having to scroll through the menu's to make adjustments. It seemed that whatever screen I last modified was not the screen I wanted to modify next. So I'd scroll to it and then make the adjustments.
I really like the preset programs that it comes with. You can make unbelievable adjustments with the XLT and I really like the ability to pick the different VDI's for discrimination. It is a great multipurpose machine.
Then the MXT came out, I bought one, the XLT ended up in the closet, and I have not missed it since. I recently traded the XLT and a QXT in for a second MXT for my wife.
I like the ability to adjust quickly and continue hunting. I like the three detectors in one concept. The frequency is low enough for coin-shooting and high enough for prospecting. For relic hunting, if you don't own a 5900(Blue and Gray)/6000/XL Pro, than this is the machine for you. It is a fantastic relic machine.
If the XLT and MXT were both out when I first got started in this hobby, I'm reasonably sure I would have purchased the MXT over the XLT for the above reasons. And, for me, the bottom line is, I'm a knob twister and the MXT fits that bill quite nicely for me.