Hemispheres is the far superior song. Musically, lyrically, structurally- it's just better. 2112 had great parts, the first two sections are pure energy. But it loses steam. Hemispheres doesn't lose anything. 2112 also has a better outro, but again, Hemispheres is better overall. It's a pretty easy win. 2112 also is not better than Fountain.
To each his own. While Cygnus II Hemispheres is quite good, I find repetitiveness and big length (over 18 minutes is too much) of that epic to be a main shortcoming. 2112 is not repetitive at all, it's musically richer and much more interesting to me.
Can't disagree TK
I love both, and Hemi has some of my all time favorite Rush moments, but 2112 has more fire, more bite when it comes down to it