Wirelessly posted (iPhone 3GS: Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_2_1 like Mac OS X; en-us) AppleWebKit/533.17.9 (KHTML, like Gecko) Version/5.0.2 Mobile/8C148a Safari/6533.18.5)
The best protection for either OS is smart user computing. I ran Windows XP for years with nothing more than a properly configured hardware router and up to date service packs and software updates from MS and I never once got any virus or malware on it.
If the user stays away from porn sites, downloading questionable content from them or other torrent sites, and is careful of what links they follow in email, Facebook, and on the Internet, they will be fine.
It's the user that is the biggest threat to a computer, not necessarily the Internet.
Practice safe browsing and OS/X and Windows can be a pain free experience.