Personally I dislike generators, they are noisy and just more work. Our electrical loads are low.
Solar works well and we charge two 6 volt batteries (lead acid) that are now in their 7th season and going strong. Our solar system is rated for a whole 80 watts.
As far as 12 volt vs. 6 volt batteries, take your pick. I would probably replace our 6 volt batteries with the same, they have served us well. Batteries don't just fail. They generally give warning.
As far as it goes, we have been in as remote an area as anyone in the US and Canada and if a camper battery fails we can keep on going without much inconvenience. We basically loose our lights and would switch to a propane lantern. For us its not a big deal.
In the winter the rules do change a little, we camp in some pretty remote areas of the mountains. we carry a small charging generator (350 watts) to help in case we had a failure of the truck batteries. We have never used it.
Skip the generator and go with a decent solar package. I will admit that 80 watts is a little on the low side, but it works well for us and if we were going to do anything, we would add another bigger panel, just to have more reserve for the rainy and cloudy days.
Good Luck.