This one was my first Leica, and even if I eventually ended up selling it I regretted the decision right from day one.
The body of the features of the Leica M4-P are practically the same of the newest M6 model, with the exception of the lack of the exposure meter.
While the absence of the meter may appear quite uncomfortable, in stable light it ended up making my pictures better and not worse.
Because I finally stopped looking at the meter and fiddling with times and apertures to compensate or something, and instead I started sticking to one shutter / aperture combination that a single reading on an external meter (or the experience, some time after) gave me.
And “magically” my pictures got better, and yes: I shooted dia with it and not color negatives.
Sure, if the light is changing fast you will end taking in and out of your pocket an external exposure meter…
So, given that the price is not so drastically different from its younger sister, the M6, I will advice to look for one of them.
But if you find a real deal on a M4-P and you think you can learn how to guess the exposure (takes a little time, but it’s not that difficult) then buy it in a snap!