The M4P is the safer buy. The first M4-2 cameras had some problems that can be expensive to repair--and problems have been known to develop with this model even if it seems OK at first. These repairs can be so expensive it may not be worth it. Both of the cameras you are thinking of seem a little overpriced, unless they are in almost like-new condition. But they are not greatly overpriced, just a little high. If you could get the M4-P for 600 Euro, I would do it. Even 650 would be all right if it is in very fine condition. But remember, you may have to get a CLA. The cost of that should be considered before buying.
I am basing my judgment of the cost on the prices here in the U.S. You can buy an M6 here for about $1100.00 That would be about 750 Euro. So I think 600 to 650 Euro would be fair for the M4-P, since it is older and does not have a meter.
Best to you,
Rob