The M4gery is the past decade's fad. Nowadays everyone wants a lightweight barrel profile, 14.5" + a pinned muzzle device, midlength gas system, 60" of free float rails, flip-up sights and the most futuristic looking & expensive stock that can hold a fruit roll-up and a spare battery or two. Seriously.
Now, that said, there's a small congregation of people coming to realize that carbine length gas is actually THE tried and true system and the alleged differences in recoil impulse aren't all that noticeable. Hatewrs will always hate...
I have rifles in both styles, but to be honest the M4 is the one I'm most comfortable with from all the years of using it. I have no need for a 20" 5.56mm rifle, but I won't begrudge anyone their choices. I just always figured if I needed more gun than a 5.56mm carbine then a battle rifle was the best path to take.