What about J4? He pushes insanely fast and has a fast escape with eq combo. I can split push very quickly and effectively with Jarvan.

Honestly, the best split pusher in the game is AP Tryndamere. This is not trolling. This is literally the entire role of AP trynd. Ignore all team fights, melt minions as much as possible, and heal from any trades you DO engage in. Massive heals, low cooldowns and decent nukes means you can duel most people from mid-late game on a 1v1 fight. Can escape from almost all 2v1 engages. 3 or more people at top means that bot is completely open. So your team either forces team fights at bot (allowing trynd to push), or 3 people rush trynd, allowing bot to be easily taken over. Seriously. Don't dis on this until you've seen it in action:

http://www.twitch.tv/qualityplayer
^ The best AP Tryndamere in the world, platinum rank. Check it. And it is literally all he plays.
Having an AP Trynd means you only have 4 people to fight with in team fights, but it also means you automatically knock over one of the three lanes. Two, if your team constantly fights near bottom.
So 4/5 or 2/3. 2/3 is a much bigger difference.