If I’m going to get just one, I like the idea of the M adjustable.
As for blades, in what I read, the Chinese blades get the most consistent praise. Sounds like a winner.
Take a look at the O clone. It s a good shaver, With a Twin blade it is a fantastic shaver.
https://www.ebarbershop.com/ebarbershop-schick-type-injector-razor-handle.html