I am voting for comfort. No one is going to see them anyway, and even I don’t think about which pair I’m wearing unless I am using the toilet. So I’m not overly concerned with pretty
Of course, comfort depends on the wearer. I’d say better than 90% of the time I’m wearing fanny flossers (aka thongs). But I’m often wearing a panty girdle on top to help flatten my bulge. I do have one nylon/lycra g-string with even less between my cheeks, but this is a special pair that acts both as a gaff and as a pair to make my boys look like girls. It works well under a bathing suit. It’s not as comfortable but it works well for its job.