The AE is nice, and excellent when it comes to slide film.
The M7 has a stepless electronic shutter, while the MP is mechanical. Because of that, the M7 has a is quieter than the MP, but requires batteries in order to be released (except at 60 and 125), while the MP doesn't need anything.
So, if you want AE, then the M7 is an excellent choice. Otherwise, the MP.
S.
P.S. I used to own an M7, and I noticed that I was using mostly like an MP (i.e., manual mode). The AE was convenient every now and then, but given I am mostly using B&W, I found I didn't need it.
Traded it in for an MP, never looked back.