I don't understand all the recent quad rail hate, it's really just personal preference. You can get lightweight quad rails like Centurion Arms, and that's without having to the extra weight of keymod sections. Which brings me to my other point, what is the first thing you put on a keymod rail? Picatinny rail sections, like what are already built in to a quad rail. You're really only saving a significant amount of weight (6 oz or so) if you run it completely slick, in which case there are even lighter options out there. Otherwise you have to also keep in mind the weight of accessories if that's entirely what you're concerned with.
Another disadvantage is that if you're not running tape switches, you have to reach up the extra distance off of the smaller handguard to fire your light/lasers that are sitting on top of the keymod sections. To me it just doesn't feel natural. On a quad rail, the distance isn't as much since your hand is resting on top of the rails.
It really only comes down to personal preference or how it feels when you shoot it. I don't have the biggest hands by a long shot, but I just prefer the feel of the larger quad rails. I also like the fact that when I mound my flashlights/lasers I don't have to reach up a mile to find the activation buttons.