"It's been nice talking with you" is a little more formal. They essentially mean the same thing, however.

I could imagine saying "it's been nice talking to you" as a speaker at a conference where "it's been nice talking with you" would require there to have been some dialogue. For example, a town hall meeting or open debate or a conversation between two people.

All the answers above are valid and correct. I like to use "it's been nice talking with you" - especially if I'm saying it to a woman. It's a little bit more "warm and fuzzy".

There is no diffirence.