As a Jungler-
Purple side can gank top easier. Purple can gank bottom from behind dragon, which works a high percentage if you don't get caught by an enemy ward at wraith/river entrance.
Purple side baron steals are easier by a LOT.
Blue side ganks bottom easier, (but oracles is a must) and has better dragon control.
Why Dragon control? Enemy jungler will be in the top half of the map most often due to the number of jungle camps there. Typically there will be 4 members of your team within dragon range vs 3 on enemy team.
In General- Blue side minions push like .01% better. Some Red said that at some point. I made up the number, it's some small percentage.