graybeard missed one point. The 1100 is chambered for 2 3/4" shells ONLY
The 11-87 will handle all 2 3/4 AND 3 inch shells, interchangably.
I have an 1187 in 12ga and LOVE it. Have wanted one in 20 since I heard they were gonna make em. Just haven't broken down and done it, yet...
I would go with the 11-87 for versatility. Everything else is basically equal.