first off i have an older 870 wingmaster (2 3/4 only) with a smoothbore slug barrel, and i would trust it at 100 yrds with a good slug like a brenneke. you might want to try some different slugs before spending a bunch on money for nothing. but as far as the other choice goes i would have to know what you want to do with it. if its a brush beater with a scope, and you are going to be lugging it around all the time, i would not use a 10lb ultra slug myself, maybe a tracker2, those are nice and light to lug around, and my son's 20ga tracker2 with a williams peep shoots like a dream. even the 11-87 would not be bad for a brush gun, and a far cry from being a 10lb monster. now to hunt fields, clearcuts, or even some hardwood ridges where you are not going to be walking around all day the 12ga ultra slug would be a great choice, so i guess it kinda depends on what you are going to do with it?? then i could tell you which one i would vote for.