These 2 watches are so strongly linked with JLC 's History that the choice of any JLC lover is obvious.
The appeal of the ultra thinness, or the friendly complication?
Not that easy, because the good answer would be " BOTH ".
If you can't afford both, then take one, and the 2d later.
Seriously, it may really end this way, because both the MUT and the Memovox are part of the JLC DNA, and as you did for Chronos, you may think that a Memo, a MUT, and a Master Chrono would be perfect together.
My thought?
Go first for the Memovox, because it is really great to wake up with a nice alarm, too.
Then you will fall in love with the MUT and its very nice Cal 849.
Best,
Nicolas

In the '90's, the MUT was a solid back. In '99, the "Master Black" series debuted with an exhibition back. The MUT silver dial with exhibition debuted in 2001 (IIRC). That's why you see both. The older solid back had one advantage: more resistant to magnetism.
-Dean