There was a heck of a debate about how tough the M16 stock was when it was first issued and lots of people bitched that it was a terrible close quarters “give ’em a smash” rifle. The reality of close up combat fighting is that at some point you may need to switch to a bayonet and fight with your unloaded rifle and use it as a baseball bat or a ram. Many of the composite materials, often referred to as Plastic by people were not very tough back in the day. Nowadays composite materials are very sturdy and in many adverse environments you are going to wish you had something other than a wooden stock. The M16 design doesn’t lend itself to be a very good smashing rifle because the weakest point really is the buffer tube. That’s just not going to stand up to being used in a harsh way without bending.
There are differences in height that need to be though about ahead of time because some of the sights out there from Troy, LWRC, Daniel Defense ect can cost you over $100 each. I learned the hard way when I picked up an Eotech magnifier and my sights didn’t work, Magpul mbus sights are probable the best priced and most durable backup iron sights on the market. The rear sight is about $50 and the front sights are under $40. Which pretty much makes them about half of what many of the Troy Sights are. Do something thinking about what you may intend to put on your firearm because sights can vary dramatically depending on what they are being used for.