I would say "gern" is more colloquial, while "gerne" is more formal. I would never use "gern" in written language, however in spoken language it is totally up to you if you use "gern" or "gerne". There is no other implications behind those two (i.e. it does not make you come of in any certain way, or does not imply anything if you use either), just use which ever feels more comfortable to you.

I myself am a "gerne" kind-a-guy :D

Both can be used, it is a personal choice of what sounds best to you. I found this hard to believe when the German speakers first told me but it is true. Oder?

when printing, I always use gern. (Gerne uses 25% more ink.) Save the planet!

as slamRN said: it is your choice. i think gerne is more formal so thats what i would use then writting a formal letter f. ex. in every say use with friends i (personaly) would go for gern. since it is a little more casual in my opinion.