Personally I think pilots should be brought more into the planning, where convenient.
Too often we are left wondering what ATC are planning for us, and would like to play a part.
I have even been given a clearance to join airways and an IFR clearance across the London TMA when I had intended to route underneath (by an over-enthusiatically helpful London Mil ATCO.) He could have saved a lot of everyone's time by just asking. As it was I was too embarrassed to say that that wasn't what I wanted and just accepted it.
But I do agree that if we are given the choice we should decide quickly and convey our choice clearly and unambiguously.