You must have a very different ruler than I do. In no way is the Colorado close in size to the Silverado. I've had both of them lifted up on my rack, pretty big difference. And actually, I would have thought the Colorado's interior, at least the driver's fore-aft room, would have been better than it is. But my 6'1" fat ass needs the seat all the way back just to fit, and it isn't all that comfortable even then. Tolerable, but not comfortable. A Cruze actually allows me more leg room.
The most common wheelbase Silverados are a whole foot longer than the Colorado, FWIW. And they can be even longer if you get the full 8ft bed (you cannot get ANY kind of long bed on the Colorado, just short and shorter).
As far as who they are marketed to, well, that is certainly debatable , but as far as who is actually driving them, I'd say around here the VAST majority of any full sized pickup, no matter its "tonnage" or source of propulsion, are driven as daily drivers with only one occupant most of the time. Majority of the fleets are actually NOT diesels, too. Sure, the big cab chassis ones often are (although not always) but many of the standard pickups purchased by companies or gov't departments are the standard V8 gasoline engine.
RAM wins.
