Styx were an abomination at best, a wind up toy designed to pop a spring and collapse on itself. I always considered them to be Grand Funk Railroad taken to the next level, which wasn't very far to go, a journey that graduates from a slow lumbering and becomes a club-footed stumble.
Kansas, though, had chops as instrumentalist and were able to deftly handle quick changes and scatterbrained time signatures with ease.
Although derivative of their English cousins through out their career, they could play the busy arrangements with the best of them; guitarist Kerry Livgren had a definite talent for this stuff.
Kansas, though, had awful lyrics, lots of them, but that was mitigated somewhat in the form of vocalist Steve Walsh, a cogent blend of Paul Rodgers and Mark Farner. His bluesy, wailing read of the band's wheat field mysticism was a welcome respite from the Brit habit of being nasal and neutered in their precise pronounciation of utter nonsense.
All told, though, not much of the progressive rock and prog rock inspired music of the era, the Seventies, has aged well into the 21st century. If this had been instrumental music, we might have had discussion of the technical aspects of the music; as is, though this genre's congenital habit of needing lyrics that are unwieldy in cadence and top heavy with the arrogant sophistry only the most isolated first year liberal arts major could manage drag this music to the bottom of the lake. The heaviness these bands sought is rather like a big chain with a profoundly unforgiving anchor .