This site doesn't count as one of the darker corners of the internet?
I don't know what kind of Sims 3 install you have, but Avast hates Origin and will stop allowing it to work properly from time to time. It's just something to be aware of if you do decide to try Avast and find one day that your game won't open.
And if you do want something heavier, as igazor mentioned, it's going to take more resources to run, not to mention it might also not like EA products. On the other hand, if you don't need the extra protection while you play, you could always disable it before launching. Just remember to reenable it afterwards.