I would suggest Norton Internet Security.
It recently scores much higher than ESET in protection based on AV-TEST.
Plus, it is very light like ESET.
Even though there are more powerful AVs like Bitdefender and Kaspersky...
Based on my experience, they have a huge impact on performance that I switched back to Norton.
Sidenote: Norton is known for its owner Symantec, one of the largest security software corporations in the world. They are not only trusted by home users but also by companies and enterprises.
Source:
http://www.av-test.org/en/tests/home-user/windows-7/novdec-2012/