It shouldn't really be which one to buy....but a matter of which to buy first!
Face it, if you find yourself in this dilema.... it just means you'll get one each eventually.
Like me! The M7, I use all the time as it is just too convenient and I'm a lazy sod.
The MP sits in the dry cabinet a lot more, it just feels good to know that I have it and only use it for street photography usually on a holiday.
Which ever you buy is largely dependant on what you usually shoot. M7 would get my vote first. Just remember, if you accidentally shoot in AE mood with the lens cap or body cap on (trust me, you will do it) it'll take about 30secs for the shutter to close again! Do not panic.
