First of all, there are tons of people who don't like Killswitch. And for good reason, they're just another melodic hardcore band with bland lyrics and a pension for terrible structures.
On to Lamb of God, who in fact, is not a very good band skill-wise. They play the most generic and least genuine variety of metal with their sub-par lyrics and cookie-cutter song structures. To go along with their intensely boorish style of play, they have probably one of the worst metal vocalists out there; the man cannot even pull off a single convincing growl without some kind of break in his voice, or is that his charm? That he can't manage to pull off something even Pantera vocalist, Phil Anselmo could.