Ranked PVP has a set of more persistent elements involved, chiefly tied to the weekly events. It is worth noting that the difficulty settings of Normal, Hard and Warlord I-IV are ignored in Ranked (it's all just Normal level), and the AI combo-breaker is disabled.
Each ranked PVP battle is worth PVP Points - winning invades and successfully defending will gain points, while losing invades and being invaded will lose points. Winning invades gains significantly more than defending does, and more than losing at either. It is currently possible to win up to 50 PVP Points from a successful invade, depending on the difficulty of your opponent's team.
PVP Points aren't worth anything except that they determine your place on the ranked ladder.
Your placement on the ranked ladder determines what rewards (if any) you'll receive at the end of the event. As said above, this is based entirely on your PVP Point total for the week.
Weekly Reset and Rewards
After one week has gone by, the current event will end, rewards will be given to the top players, and the leaderboard will be cleared for the following week's event.