Neither of those computers are a good choice if you want to use dual monitors. The basic problem with them is that they use intergrated graphics, and neither of them has slots for PCI Express video cards, or even AGP cards. Either computer might support dual monitors if you installed one or two PCI video cards; a single card configuration would require a card designed to support two monitors.
I run dual monitors. I have two video cards installed, one AGP and one PCI.
How do you want to use dual monitors? Do you want to be able to clone the primary monitor on the second monitor? Is you primary interest being able to have different apps on the two monitors? I can not clone; a single card that supports two monitors is required for cloning. That's not an issue for me since I don't care about cloning. My purpose is to run different apps on different monitors; my two card configuration does this well but, as far as I know, single cards that support multiple monitors work equally well for this purpose.