I never gotten the chance to see either ELP or Yes. Oh, you really missed something then. (And I've certainly missed opportunities to see other great bands). Both were amazing. (it's also a bit humorous to see the different outfits that Yes members wear!)
Actually, the two greatest concerts I've ever attended were Jethro Tull and Alan Parsons. Ian Anderson is a true performer....and yes, the Alan Parsons Project totally shocked me with how well they performed on stage.
Kevin