Firefox reigns over both for me.
Chromium is severely lacking in many features but it does things smoother than Safari/Webkit does for me. I still have Webkit in the dock but I almost never load it up. I've grown to FF recently but it's my alternate identity browser for junk and games mostly.
You do know Chrome uses Webkit too, don't you?
The latest builds of Chrome are pretty nice and web browsing is definitely fast.
But.
There are a lot of bugs, random window redraws, floating tabs, and my wonderful bookmarklets don't work. Oh well.
Once it is release, I will definitely definitely give it a go again.