Hi Velo,
I am a newer C-Dory owner myself, but will share what I have gleaned. The 16's are nice little boats, but most folks on here have 22's or bigger, so threads on the shorter hulls don't get much traction.
I'll touch on years first, then the crack you mention.
The biggest difference on the 16's is pre- and post-1987, which was I think the only year they made a significant update to the C-Dory 16 before they stopped making them in 2020.
Pre-87 boats are referred to as "Classic" hulls. What most people notice is the short pilothouse (post-87 they introduced a longer cabin) but the two biggest differences are in the hull. First, classic hulls have almost entirely flat bottoms, like a clothing iron. Second, they have no splashwell at the back; instead there's just the transom.
After 87, they introduced a version with the cabin two feet longer (and the cockpit two feet shorter) called the C-Dory 16 "Cruiser"; they kept making the one with the shorter cockpit, but post-87 called it the "Angler" (bigger cockpit = more room to fish). More importantly, they added just a little bit of vee in the main hull and added a splashwell.
Where those changes matter is in seaworthiness.
The C-Dories have plenty of good characteristics, but their two worst are their tendency to pound and the way the stern gets pushed around in a following sea (and "slides" in turns), with a close third perhaps being their tendency to dig a chine if not trimmed attentively. I have not personally ridden one of the newer hulls, but it's not rocket science that a touch more vee probably improves all three.**
The second addition, the splashwell, also isn't rocket science. The Classic hulls have a pair of low "seats" in front of the motor; post-87 they have a bulkhead there, so the seats are replaced by a self-bailing motor well. In a Classic hull, any water that comes over the relatively low transom is now in the bottom of your boat.
In my mind the splashwell is hands-down the biggest improvement. But again, what people gravitate toward is the 'cruiser' cabin, which in later years featured much nicer finishes, up to and including cushions in its dwarf-sized vee "berth" and a pull out camp toilet.
Some good threads on hull changes over the years:
http://www.c-brats.com/viewtopic.php?p=108472&sid=70c06c9988c8b1848f981ceee7539bec
http://www.c-brats.com/viewtopic.php?t=7882
http://www.c-brats.com/viewtopic.php?t=29025
http://www.c-brats.com/viewtopic.php?t=2523&view=previous&sid=b7958fd15c66cb7a800168eae0de101b
http://www.c-brats.com/viewtopic.php?t=896
**One thing that did change over the years, I think moreso on the 22's, was that the company played around with different arrangements of strakes, I suspect mostly to try to tame especially the tendency to slip sideways when trying to turn on a plane.