Both are a grind. I'll say NCAA Hockey is more difficult only because the sport lends itself to more upsets (see 1996-97 Michigan, 2010-11 North Dakota).
I will actually say with all the conference shuffling in both sports that I'm more excited for football. The loss of the Minnesota and Wisconsin hockey series' to me is a big blow to the schedule, while the football schedule is loaded with quality. Just my $0.02.