Some of my clients prefer the canonical link. But I don't because exectution of the canonical tag is up to the search engine. If I don't even let them crawl the content in the first place, then the whole thing is a non-issue and Google can't mess it up.
I always prefer controlling what I can on my own server rather than throwing it into that immense pile of data that Google has to play with. I know very well that "stuff happens" when you've got a huge database, and Google's Caffeine infrastructure is far beyond what I can even think about very well.
I also don't want to see different "sort" variations crawled at all. I don't want to use up the bandwidth or the crawl budget.