Windows in virtual machine - XP or 7 ?

So I have a couple of programs I need to run in Windows on my Mac. They're not anything so special that I need to bootcamp to use them, a virtual machine is enough. It's simply Outlook (Outlook for Mac seriously is awful) and some Youtube Downloader which is Windows only. So my question is, XP or 7 ?

I know very well that Windows XP now has no security updates from Microsoft, but the fact is my MacBook has 4GB RAM. Windows XP will run far better with 1GB RAM in the VM than Windows 7 I think. Maybe I'm wrong and I'm willing to be told that, but what do you guys think ? Is using XP with the risk worth it so I have a gain in performance ?

Thanks !