I need both a 4.5" for precise cutting and a 7" for more aggressive weld metal removal and surface prep. I've used the hell out of a Hitachi 4.5" grinder and it's still hanging in there well. I also am a fan of Makita super thin 4.5" cutoff wheels because they cut through steel quickly (though they wear down quickly too). A Makita 7" angle grinder is hard to beat for bulk material removal. I recommend for either that you buy a pair of kevlar lined cut resistant gloves and a face shield because it's better than any pair of glasses.