For many people, a DRO is a luxury and not a necessity, but when it comes to a mill there are a lot more features in the MX-200 DRO's in multiple menus, soft keys and graphical representations of arrays, bolt circles, and if desired touch probe that for the cost difference between the MX-100 and 200 there is a big difference in features. Simple things like feed IPM simultaneous as well as a 0 indicator, I use quite a few of the DRO features.
As far as the capacitive touch screen, I prefer sealed membrane switches as far as tactile feedback, but it is more reliable than mechanical switches. I have heard other's complain about the switches on the EL400 (MX100). With a screen protector on my El700, the capcitive touch on mine seems to be less finicky as to finger placement. On a mill DRO, if you spending that much I would recommend a graphical display otherwise if just for numbers save some pocket change and maybe get something less expensive. Lathe, you are just reading numbers, but I still prefer the less expensive ES-12B over the MX-100L. Whatever floats your boat.