I use both Magpul XTM rail covers on the sides and bottom rails and ladder covers on the top rail on my two carbines.
Ladder covers pros: Lowest profile, easy to cut and install, and covers sharp corners which are more comfortable to hold with the bare hand
cons: Virtually no protection at all on impact with hard surfaces, doesn't insulate against heat like rail covers
Rail covers pros: Better rail protection, insulates heat, some brands are low profile and have non slip ribs like the Magpul XTM
cons: Fit on rails vary some brands fit tight some very loose, panels have to be cut for better fit, some brands too thick and bulky