Between the 1100 and the 11-87, the heavier gun will "kick" less. My 1100 has a mercury filled canister in the mag tube to reduce kick and smooth the swing.
IMHO, the main advantage of the 11-87 is its stainless mag steel tube. Anyone who's worked with 1100s knows the problems associated with a mucked up mag tube.
Some target shooters say the 1100s are more reliable with light loads than the 11-87s. Also, they don't like the 11-87's long chamber and feel. If you want a gas gun that will shoot a wide variety of loads and kick less, the new generation of Berettas have it all over the R-1100/87s.
Now, can you tell me why the 1100's don't need a glass lined forend. I don't know but perhaps you do
Curious, my 1100 has a glass lined forend. Is it because it's a target gun or does it have to do with the year of production?