Kind of a Ford vs. Chevy vs. Dodge thing... MagPul has quite a variety of stuff, but I don't know that it's any better than some of the other stuff out there for sale. The things they do have going for them are name recognition and availability.
I think it is more of just personal preference!!! I'm not running any Magpul furniture on my S&W but I do have a buddy at work that switched his out for Magpul furniture on his and he likes it but their again that's just personal preference because he said he just liked the way their furniture looked!!!! The only thing I have switched out on mine is the forearm I put me just a cheap UTG quad rail on mine so I can add a light to mine because mine is being used as a home defense tool other than the forearm mine is bone stock!!!!
I do run nothing but Magpul P Mags though I love them and never have had an issue with them!!!!
I used to be a 20rd aluminum GI mag man... never needed anything more. Until I tried a PMag. Now I'm swapping out all my 20rd'ers for 20- and 30rd PMags.
I never considered myself a Magpul fanboy, but they make good hardware. I have a Magpul grip (because it fits my hand best) and a Magpul handguard (because it has a triangular profile very similar to the A1 handguards I had in the Army, that I prefer over the round A2.) Beyond that, it's whoever makes what I prefer. Tapco makes a very nice collapsible stock (I've installed 2 of them on other builds, very solid, $69) for instance, so don't be wedded to just Magpul. The problem is... unless you can handle the hardware you are interested in, you don't really know if you will like it or not, or if it's solid or rattily or not, etc. just by looking at it in the package.
Got a specific model you looking at? I have magpul stuff on my rifle and like it. I have a ctr adjustable stock, moe midlength forend, and moe pistol grip. I like it all. Sturdy, well made, and light. They are simple and tough. They have served me well so far.
See if you can find someone with the same furniture on their gun and then decide if the feel is worth the $100 or so. I re-fitted a DPMS AR-15 for a client a year or two ago, and really liked the feel of the Magpul furniture. And the P-mags are the ONLY type I trust my life to, I use all the others for practice only these days. I'm not really a Magpul fanboy, but I've liked everything of theirs I've tried.
I have a PRS on a 20" RRA Predator Pursuit and several PMAGs. All exceptional pieces of gear. Unlike the others I'll admit I'm totally in the bag for MAGPUL. It was found by a Marine, what more do you really need to know?
The "Mindset" tab on the website is worth the price of admission alone. I feel I owe them money for putting that up there. "The barrel of a .45 says no in every language." "If you can see the big picture, you're not focusing on the front sight." "DANGER CLOSE know no atheists." And many more gems of the like just there for you to enjoy.