Suarez was never a liability in terms of red cards. In fact, he has a good discipline record in terms of fouls and cautions/dismissals. His bans were for other things, i.e. the Evra affair and the Chiellini/Ivanovic bites, which were picked up by TV audiences latterly.
Diego Costa's gnarliness and needle makes him a better player. That's a certainty. If you take away that edge to him, and the edge Suarez play with, and you have an inferior athlete. Unquestionably.