NIS is so streamlined in its efficiency it's sometimes a boring product to discuss

Powerful ability, lightness and excellent usability...
BitDefender's idiosyncrasies on the other hand can be talked about at length. They tried to take a leaf out of Symantec's book and introduced 2012 product lines with improved usability. At least that was the intention, which sadly was initially let down by serious functionality issues and far-from-excellent performance. Kudos to them for managing to turn that page and improve the product considerably. It's very stable now, low on system resources, no major performance issues [some browsing speed slowdown aside]. What has always been known though, is their excellent AM engine.
Where they're still falling behind Symantec is their cloud infrastructure and intelligence [take the stand-alone TrafficLight, for example - it still relies heavily on local AM definitions] and, not so unimportantly, the quality of their support [not a reflection on the committed and hard-working team members].
An accomplished and quiet achiever, NIS gets my vote.