My collection consists of Weta/Sideshow Environments displayed along the representative ToyBiz characters and their matching Sideshow Helms from the Sideshow Helm collection.
I have decided not to pursue Sideshow statues, I never liked their lack of scale and their dolls like faces, instead I decided to stick to ToyBiz characters which they all follow good scale patterns. (6 inches height for men, 7 for elves, 10 for Trolls, 4 for Hobbits).
I own all the LOTR Toy Biz characters and nowadays I combine them with the shields produced by Weta.
I only own certain statues of Sideshow, mostly of creatures that sort of match (at least visually) in size with my ToyBiz characters. Therefore I own Shelob's statue, the original "daddy" Balrog, Mumak of Harad and the Watcher of the Water.
I do not own Sideshow Cave Troll as I rather prefer the Trolls made by ToyBiz!!! I have 2 armoured trolls (the ones that open the huge black gates with their chains), one Attack troll that is displayed matching his Troll Battle Helm from Sideshow and one ToyBiz Cave Troll which has better face detail, body posture and even sounds compared to the very expensive and much bigger in scale Sideshow Cave Troll.

I do own The Stone Trolls and the Combat Troll, they are smaller than the Toy Biz Trolls but not that much, I think I can do something about it, plus Stono Trolls is too good to let it pass.