Fords vs Chevy's. Boxers vs. briefs. Red wine vs. white wine. Life is full of choices.
I have a green filter. I don't use it often. But if I encounter a situation where it might be useful, its there. The incremental weight of a Cokin filter is trivial (expecially in a pack that weighs 30+ pounds), and the CD case that I use to hold fiilters has lots of empty slots.