The best brand without a doubt is hilti, but not all their range and they are very pricey, a guy i used to work for had, 36v hammer drill & 14.4v impact drill, 14.4v combi drill. quality in every way, i owned a te-2a 24v hammer drill, absolute tripe, batterys didnt hold a charge, dont deserve to have hilti prited on them.
when it comes to 24v hammer drills, the bosch gbh drills walk all over the makita and de walt's and hilti's
18v and smaller, makita all the way!!