You can play free or p2p. If you p2p you get access to additional servers with 2 and 3x exp, increased drop rates plus other benefits. The p2p characters can log onto either free or p2p servers so the free players will find it hard to compete.
The Free edition is a good way to see if you enjoy the game first before putting a little money down to play. I would say check it out and see if you like it first...