Dual-booting is a software thing, nothing really to do with the processor.
Are you talking about installing 2 operating systems on your computer, or running one inside the other using some kind of virtual machine?
If it's the former then you'll get no specific performance increase other than the fact the Core i series is generally superior to the Core 2 series.
If it's the latter then you want as powerful a processor as possible, so you may be better off with the Core i
What are your processor choices?