I don't mind dining with a group and we have had some wonderful table mates. The problem is dining at a fixed time during the cruise. I do not enjoy having my activities dictated by what time I have to eat. With alternative dining options we may only eat in the dining room three or four times on a seven day cruise.
If, for some reason, you aren't going to make it then you need to inform your dining companions and the Maitre 'D that you won't be there so they won't "wait" for you. You may not see your dining companions until the next night and often, the night before, you have no idea if you are going to eat in a specialty restaurant or not. We've informed the Maitre 'd a few times and it seems that about half of the time the information never got to the waitstaff and the table mates waited for us. This was one of the reasons we switched to open seating.
Even in open seating we don't mind sitting with others and having some nice dinner chit chat.
There are times, especially after a long day ashore, we just want to eat and then relax. One thing my wife and I have no problem with is having a conversation. Even after 30 years we still find something to talk about.
I like to have "options" and not succumb to the herd mentality. The regimentation is what almost stopped us from a cruising a few years back.
If I am with my family, it would be at least six people, so I have to say that I would prefer to just eat with them and not have two people feel somewhat left out.
If it is just my wife and I, and it's open seating, I have to go with #3.