I own the PM9 and P380. The reason that I own the P380 is that I don't find the PM9 to be comfortable for pocket carry. While there may not seem to a large difference on paper, they are VERY different when it comes to pocket carry. The P380 is significantly lighter when fully loaded and it's slimmer dimension makes it print less, especially when you add a holster.
Your best bet would be to go to a gun store and try to fit each one in your pocket to see which one is more comfortable. If you have large pockets, the PM9 may work just fine.