Floppy is more of a cute char. I usually make my chars strong and serious so they have upright ears. Can't really have squishy mushy stuffs in my fics because those are the kind that I simply must kill in a chapter or two.
All of my characters have upright ears because of their species (in this case, a lynx, a wolf-husky and a creature that is part bat). Nashida, my lioness, I guess it could be argued that her ears don't really stand straight up.
I have no particular preference in ears other than they should match to their species if possible, or have a reason as to why they don't (ie a GSD with a floppy ear because the cartilage was damaged when they were working). The majority of my characters have upright ears - but that is because their species/breeds tend to have upright ears. I do have a saluki with ears which hang down - although that is typical of the breed.
Also of note to point out - the majority of wild, non-domesticated species which have ears, have upright ears. There's only a few exceptions. Floppy or folded ears tends to be seen more in domesticate animals. Being as there are simply more species of animals to choose from which are wild, it follows suit that there would be more furries with upright ears.
I prefer upright ears, I just think they look a lot better. Of course, there are some 'sonas that suit the floppy ear thing (can you imagine a spaniel without the fluffy ears hanging down?) but generally the upright kind just look better
Would of been interesting to attach a poll to this one, get a better look at the opinion split.