I love M&P's and have a half dozen or so. So I would like to add the Shield X to the collection but for the life of me I don't see the purpose. For range guns there are better choices since concealment isn't an issue, and for a Carry gun it might be a hair slimmer than the Shield Plus but it's also longer and taller. The capacity of 15 to the 13 in the Shield Plus doesn't matter much, especially when you can use Equalizer 15 round mags.
I'll probably stupidly buy it and shoot it once and then never again since I have so many others to shoot. I have guns I haven't shot in years. A few I have had 3 years and still haven't shot.