I did a test on a single client machine since I assume that's what you were doing the controlled test on.
Symantec took only 2.6 MB of memory scanning over 200GB of junk I put on the computer, with every option turned on (just a bunch of mp3, random exe, videos and documents I copied and pasted over and over again). If you want to get in the nitygrity it also took another 4 MB for the systray icons. My 10 MB comparison was from the test we did at our lab when we were doing remote scanning under a managed antivirus system, sorry for the confusion.
You are right, index doesn't always mean it's better. I was just saying it was able to do it faster because it had the engine built in. When it's on it does a differential sweep of the system. But when you check every option to do a full 'fine tooth' scan, it doesn't apply to the sequential daily checkups. Anyway, the full scan took about 14 mins under full options.
Symantec's solution actually detects more than NOD's AV. I don't have time do intentionally put viruses/malware on comps to test that out but general reviews all over the net state so with great detail. So I would have to stay with Symantec offering better protection. As far as lower footprint, my tests show managed or unmanaged, Symantec still is lower.
The antivirus package test we did was at my job, in a controlled lab, where we test several software titles before implementing them in our network. Just because I happen to be the only one, before, to stand by Symantec doesn't mean I work for Symantec.
As far as which one is better? I think I said they were about the same before and maybe gave the hint that Symantec is better later on, either way they're both the best on the market today imo with Symantec a bit in the lead.