Vista - Eset Smart Security 4 or Norton 360 3.0?

I certainly wouldn't touch anything Symantec. Norton used to be good when it was Norton but like a lot of things it got bought out and the buyer started to make it into something no sensible person would want.

That being said I've hear that the latest versions are not as bloated and apparently do their job well but I still wouldn't touch them, too many horror stories on the NG's and Forums.
Myself I use NOD32 v4 alongside Windows Defender the Vista firewall and SuperAntiSpyware Pro. Until recently I also had SpywareBlaster on here but as I'm now running IE8 feel there isn't the need for it anymore.

Of course one of the best solutions in security is common sense and Safe Hex

just switched from Norton 360 as it just became too taxing on my pc and ran in the background whilst I was working making it grind to a halt. Switched to Bitdefender which is cheaper and all I would say what ever you do, if you switch from Norton, make sure you use their uninstall tool or the moment you instal another AV Nortons firewall stays up and runs along side the new one causing random restarts.

I'm not sure how Norton isn't classfied as Malware

I use Norton IS09 on 3 systems and Kaspersky IS09 on one system. Both are excellent with very little intrusion. But I have also heard a lot of good things about NOD32 - but never used it myself.