Problem is, however much you pay, or don't pay, when a new virus comes out, there are hours or days before any of the anti-virus firms have had chance to analyze the effects, and patterns within the software to have a 'fingerprint' with which to identify that virus.
So you pay nil, or 50 or whatever, and neither of them will detect the virus if you happen to get it in the first couple of days.
As for Norton, it is something I'd avoid these days, as they made their s/w so deeply embedded in the machine that not only would some not uninstall with the CD, but eventually they had to bring out extras on their website to help people wanting to uninstall their s/w. Went the way of products from other big software corporations and became an all-singing all-dancing, and is something I'd give a wide berth.
When it was Norton (software by Peter Norton) it just got on with the job, but I think Symantec that bought up the firm/brand has been like a kiss of death. Gets lots of usage no doubt because they put it on millions of new PCs as a free trial.