Microsoft SE vs Norton All-In-1 360

So, I have a choice.

Not sure which Anti Virus I should choose.

Microsoft Security Essentials?
or
Norton 360

I know Norton 360 is pretty expensive, but we already have a 2 year license, though 3 computers are already used, it still won't be too much to add on one more pc.

I also noticed Norton has become a LOT less resource intensive in their latest version, meaning my PC won't really be taking too much of a hit.

I just wanted to hear your guys opinion and personal experiences.

thanks