You don't get any experience or any increase on your stats. It's a correct one, so don't expect go get any.
What you get from PvP challenge is
fame. The experience you see in the battle report is actually fame.
Fame affects your fame rankings and also overall rankings. You can see them in the statistics (players ranking). It won't affect anything to your hero, ~except that you are become more popular amongst other players
~, but it serves as alternative objective in this game. Many players chose to do PvP over time to get the top of the ranking.
The reason? Self satisfaction and fun. What else do you want from a game except those.
Last, you can see your previous PvP fights in your profile. Click the "Challenge" above your battle records to bring out your last 5 PvP challenge fights instead of dungeons battle records.