If you're going to ask on an internet forum, you're mostly just going to get techy geeks who defend stuff like Linux and Windows XP because they are popular for customization and 'alternative applications' (aka applications Windows doesn't support).
However, for stability, its been proven both Windows Vista and the new Windows 7 are MUCH more stable than Windows XP or Linux. As well as having a TON more features and pretty much being idiot proof. Whereas you need to have some technical knowledge to use previous versions of Windows and of course Linux.