I don't have the Tull, but I have the other three.
BSS was one of my first prog albums, it has some great songs. As always with ELP, though, inconsistent- I'm not too keen on Benny the Bouncer. Karn Evil 9 is pure, raw energy, and the second part (Emerson's solo) is amazing.
Octopus is kickass. So perfectly orchestrated, all the parts go together well.