Unity3d on an older mac performance?

I'm looking into buying a used mac book/mac book pro for unity3d mac & iphone 3d games development for fun. I can't afford a new mac but I see some nice low price 2006/2007 mac books and mac book pros on ebay but as I'm completely new to mac I don't know if they will do.

Question 1: Would a 2ghz core2duo 2006 mac book (not the pro) be capable of running unity3d smoothly?
Question 2: Would there be much of a performance increase with a 2006 2ghz core2duo mac book pro instead?
Question 3: Which is more reliable, I've been reading about gfx card issues on the pro?

The system requirements are a very modest…

System Requirements for Unity iOS Authoring

An Intel-based Mac
Mac OS X "Snow Leopard" 10.6 or later… And so any old Mac will do.

http://unity3d.com/unity/system-requirements

The MacBook Pro would offer minimal performance increase which would not be enough to justify a large price premium over the basic MacBook but for a little more would be a better option.

Both are solid reliable machines. The Pro uses a Radeon X1600 graphics processor which is well established and should not cause problems.

http://www.amd.com/...x1600.aspx