You answered your own question.
-The Mk9 worked but was too heavy (23 oz).
-The CM/PM weighs in at 14.5 oz.
If you want to pocket carry, the CM/PM will work very well. The Glock weighs what the MK does, and is fat as well.
Don't get me wrong--we both know that Glock builds an excellent firearm. But not all of us find the "Thick as a Brick" easy to conceal...and for pocket carry, any double stack is a non-starter (IME).
There is no law against owning one of each (not yet, at least)...and the best reason for owning more than one is to fulfill different requirements. Doesn't mean that this one is good or that one is bad. It is whatever works for you.
I have owned a G23 and a G19, and although both are gone, I am currently looking for a G20SF.
I have also owned a PM9, a P45 and a PM45, and still own the first two.
Each has its place. If you can only afford one for the time being....choose the one that can perform the most roles at one time, and expand from there.
Enjoy your search.