Goo-goo, so here's the deal.
On the Definitely Maybe set (by the way, the three are called the "Chasing The Sun" versions), you get all the b-sides, plus "Sad Song", except, it doesn't have the live version of "Bring It On Down" from the "Shakermaker" single. (You also don't get the full original Creation demo, which I would have liked to have heard). There are also two download only tracks - "Live Forever" and "Digsy's Dinner" from Glen Eagles in '94 that aren't on the CDs; I'm going to try to find them myself, I'll let you know.
On the (What's The Story) Morning Glory? set, you get all the b-sides, plus "Bonehead's Bank Holiday", except, it doesn't have the live version of "Live Forever" from '95 from the "Roll With It" single. You do get the "You've Got To Hide Your Love Away" from the Japanese "Some Might Say" single. There are also two download only tracks - "Hello (Demo)" and "Wonderwall" from Knebworth that aren't on the CDs; I'm going to try to find them myself, I'll let you know.
On the Be Here Now set, there's a fair amount missing. You do get the Mustique demos, which are cool, but you don't get "Angel's Child (Demo)" or "Heroes" from "D'you Know What I Mean?" single. (Don't quote me on the Angel's Child; I don't know if that's the same as the Mustique demo version; I have yet to compare them). You don't get the cover of "Street Fightin' Man" from the "All Around The World" single, and you don't get "Cigarettes and Alcohol (Live)" or "Fade Away (War Child Version)" from the "Don't Go Away" single. Not crucial misses, though the "Heroes" and "Street Fightin' Man" are solid covers.