What do you want to play? If all you're playing is League of Legends on Low/Med, Minecraft, cheap indie games off steam then you can can go with either. If you wanna play slightly higher spec'd games like Starcraft2, Diablo 3 (will sputter when more than 20 mobs are on screen), Civ 4, etc etc then i would say you MUST get the GT 840M then.