Separate RAMs or Single RAM would result in better performance with intel

Hi,

I want to upgrade my RAM to 4GB from 2GB. I am using an (intel inside) computer. Wanted to know which would result in better performance with intel. Two separate 2GB RAMs or one 4GB RAM or it doesn't matter whichever, the performance is the same.

Thanks.

P.S I don't know if this will be a relevant question here though but in my view this would be the right place to ask as this is related to compatibility.