The real world, but it is also more rewarding. A virtual friend requires little or no attention form us, think about it, when we chat online, we are also doing many other things; homework, surfing the web, working, writing a thesis. Whatever it may be, we are not fully concentrated on the conversation.
In the real world, if you are talking with someone, and trying to read a book at the same time, then you are undoubtedly missing parts of the conversation and the book. In addition it is considered quite rude. So our entire attention span must be focused on that person.
As I said real relationships are much more rewarding, because they are the naturally occurring relations, and they require more input form us.