at least its nots as much of a beast as the older m11 and m8. held one of those and was like YIKES that a lot to hold up.
i still use a lanyard with whatever radio , even when i had the mt4 just so i wouldnt drop it but the old school m11 was almost a requirement ha.

when i got the mt4 the first impression was how rediculously light it was.. it felt like a toy quite literally comarpred to some other radios i had in hand.. futaba 3pks, AE XP3 spectrum dx3s.
the plastics have a nice finish, but i discovered how thin they are in spots when i accidently ripped the lanyard loop out one night when i was stretchin on the stand. not a big deal, but not a well designed bit.

finish was pretty good but the area around the switch was kinda messy. sharp ect. also the cover over the screen is quite thin and deformable. im used to the futaba with the thick plastic cover over it.
cant speak for the m11x but the m12 is no better in this department. the plastics feel robust, but probably the same plastic. just seems a little more finished, though that thin plastic screen cover is still present.
I liked using the menu a little better than the m12. the wheel has larger cut outs that feel nicer when you scroll for whatever reason, and the menu makes good use of the up down scroll motion.
the m12 has a left right that is like a early 90's microsoft mouse.. the clicks that would get you kicked out of the library for sure ha.

i was disappointed in the no drop down with the mt4, but honestly, unless your a real feel snob, you can do without it. the radio is so small in your hand you really dont need it .
the m11x you have definitely has more features and with the right receivers is faster. i dont think the mt4 would be as fast even if paired with a rx471 but would be pretty close.
the mt-4 is a great radio though which has all the truely useful features any racer needs. i really really really didnt need to upgrade to the m12 and didnt get faster as a result. maybe a little more consistant as the radio is just a tiny bit more comfortable. the response surely helps but we are talking tenths of a second at very most. maybe a driver with more experience than me would notice more. of course a faster servo would be even better still.

ps, you mentioned your girl is all into rc and i am jealous... my wife considers my toys junk that needs to be cleaned up if i happen to leave any of it around =( maybe i should trade her in