The glaring difference is that with the 1100, you're limited to using 2 3/4" shells compared to the 11-87 which allows for 3". I honestly don't know if they use different gas systems as I'm a pump guy myself, but if you're looking for lower recoil from the get go, I'd say look for an 1100.
I'd have to check their website but I think the 11-87 offers more models in varying configurations, depends on what you'd use it for most.