Render conundrum.

Hello, i would appreciate some feedback on this question of mine...

If you use a second hard drive to store your media files you render faster then if you try to use the same hard drive as you have the FCP and OS stored on.

I have two mac books. One has a quad processor and one has a 2 duo processor. They only have one Firewire 800 port each. So should i use that port to connect to the other mac book and take advantage of it's processors, or use that port to connect to an external hard drive so that the one hard drive isn't doing all the work? Or is there another configuration that would work better with this scenario?

thanks!