Does Snow Leopard have a lower version of Safari than Leopard?

I'm just about to upgrade from Leopard to Snow Leopard and browsing through the booklet that came with it I saw that it says it contains "Safari 4." They advertise this as though it is an improvement, but I currently have Safari version 5.0.6. Is it possible that Snow Leopard uses an older version of Safari than Leopard does? If so, will it downgrade my version when I install it? How could I prevent that? Or could I upgrade Snow Leopard after installation to run Safari 5 or more? Is there a big difference between the two versions? The whole pont of the upgrade, of course, is to get better, newer versions of everything.