If you have a full-size now, I think over time you’re really going to miss it and become annoyed with going smaller. Look at how spacious crew cab seating is now and you won’t have that. When you can’t fit everything you want in the bed, you might have to tow a utility trailer, etc.
Think long and hard about it and I’d go to the car show and just sit in the Colorado/Canyon for a while and think about it. Stare long and hard in that bed.
The mid-size trucks have come a long way and are just as powerful and share other specs with the full-sizes of the early 2000s and before, but my point is that now that the full-sizes have improved so much, you are going to miss out on all of that. The biggest being is the roominess in the cab.