They both are free and offers awesome services but i prefer using windows defender because of the name, it's issued by Microsoft which is a goodwill for them.
Does my msn id appears in Skype when I logged in, otherwise all this process is meaningless. I have lots of contacts in it and use MSN messenger on a daily basis.
Re: Comment.. Windows 7 has this bug and didn't resolve this yet, for this purpose i start using the Realtek because it's really better to manage this LAN and wireless connectivity.