Proper covers like TangoDown (My preferred) or KAC will help to keep your hands cool from the heat of sustained fire. The ladder cover merely protects the rail by filling in the slots, and won't do much for protecting your hands. If you put more than five mags through your rifle, I'd recommend rail covers, and not just the ladder covers.
I use KAC panels on the sides and bottom, and ladder covers along the top, to protect the rail from a beating.
Thanks,
Brad