I can only really compare Miami, Charleston, and Jacksonville, but Miami cruises definitely have a more diverse crowd, many people flying/driving in from all over. Definitely more Latino cruisers and they kept the nightclub hopping almost every night until close, we saw numerous Quinceanera's onboard as well. You had all levels of people dressing up (or not) every night. Everyone seemed friendly and happy to be on vacation and wanting to party. Charleston and Jacksonville almost everyone is driving in. I'm sure there were some who flew, but I don't think I ever met a single person who flew to either of those ports, which makes sense because if you're going to fly, you might as well embark somewhere with lower fares or a more interesting itinerary since the cruises from both of those are predominantly some variation of Nassau/Freeport/Half Moon Cay/Grand Turk.
Charleston cruises were probably 80-90% full of NC and SC residents each time with most driving in the morning of departure. Everyone always very friendly and polite, easy to strike up conversations, etc. The overall vibe of the cruise really depended on if it was over a holiday/spring break or not, length didn't seem to affect it much. Granted 5 vs 7 days isn't much of a difference. A couple New Year's cruises definitely had more people onboard interested in staying up late and having a good time the whole cruise. Spring break more families with kids, everything quieted down by midnight except for the casino. In general, everyone was super laid back, people tended to dress up nice on formal nights but pretty casual the rest of the time.
Jacksonville cruise was similar to Charleston in that it seemed the vast majority drove in from the Carolinas, Georgia, or nearby in Florida. Over spring break so a lot of families with kids, everything pretty quiet by midnight or so every night. I did witness more people with attitudes/being rude but apparently that cruise was almost a type of "training cruise" according to a crew member so there were a lot of new employees who were still learning, unsurprisingly this resulted in more hiccups and less stellar service overall than we've had in the past. Didn't really bother us, everyone has to learn and start somewhere... but it did seem others were less than enthused by this, although I suspect that would be the same regardless of port.