Sabbath
Rush had A Farewell To Kings and 2112 as their best 70's albums. I'm not a fan of Hemispheres, Caress of Steel is weaksauce, Fly By Night is good and their debut is uneven. Meanwhile, Sabbath had Paranoid, Master of Reality, Sabbath Bloody Sabbath, and Sabotage. Sure none of those reach the greatness of AFTK or even 2112, but even the albums I didn't list are good. Vol. 4 is a good album, the debut is pretty good and even the last two Ozzy albums have some good tracks here and there.
Sabbath wins out for sheer consistency here.