The one on the left is a US pressing and the other is a UK pressing. The US pressing has the annoying text in the upper left corner and the photo is slightly under-exposed. But what really bothers me is the blank white square above the "PINK FLOYD" text at the bottom of the cover. The UK cover shows the blank square as the soundtrack album of Gigi. For me this omission ruins the great cover designed by Hipnosis. Only very early US pressings of Ummagumma show the Gigi album. It was quickly removed from later pressings because of copyright reasons. Pressings in other countries retained the Gigi album on the cover. I had never seen the complete cover until I came across a UK pressing in a record store in Soho a few years ago. The copy wasn't in good shape. So I passed it up. I've been on the look-out ever since.
When you've been collecting records as long as I have, it's no longer surprising that you'd be luckless finding a specific album for years and then within a short span you'd come across multiple copies. So it was last Sunday at a record swap that I came across a near mint copy of an original German pressing of Ummagumma with the Gigi album on the cover. I didn't hesitate to buy it. At the same record swap, I found a late 70s UK copy of Ummagumma, shown above. I bought that one, too. Why? Because I found it to be doubly satisfying after all these years of having gone without.