Is Norton still worth it?  Or just Avast for free or something altogether different better?

I've always had good results with MalWareBytes...

Avast or Bitdefender.  Avira is also really good but the free version has nag screens.

malwarebytes is good, but isn't an antivirus software. It's anti-malware (which technically includes viruses by definition, but in practice they focus on different threats). I'm not sure what the latest malwarebytes extra-awesome-premium-suite offers, but traditionally, it's recommended to use MB in concert with some kind of antivirus software for a layered approach. 

Personally, I just run a malwarebytes and avast scan if something seems funky on my laptop, but never have any active protection (I especially hate when AV software wants to scan all pages/websites/emails/files/folders, etc that I am trying to access as I'm trying to access them. Makes for a clunky user experience). I've not had any real issues in many years. I do run ad-blocking software and avoid clicking on anything that I'm not specifically looking for, so that probably helps. 

My interpreter in Afghanistan asked for my help because his computer was running really slow and doing weird things. When I sat down to look, he had a bunch of pakistani porn tabs up in the background and a crap ton of randomly installed malware from all the shitty links he was clicking all day. MB removed something like 1500 files, Avast another thousand or so, and I had to get some other specialized tools to uninstall some of the little buggers that had latched onto his system. It was still probably infected with something. I recommended he just reinstall windows, but he was happy with the relative improvement, so... back to the pakiporn. 

Here's some info on the differences. 

 
What’s the difference between antivirus and anti-malware?

ive been using windows defender for a few years now with no problems

Same. It's worked well for me.

Just migrated to System Center controlled Windows Defender in my multi-thousand user environment. Working well there also so far.

Windows 10 Pro

Good recommendations so far, thanks, guys!

Bitdefender.

Check out the anti-virus tests. Bitdefender is always either top of the heap or very close to it. Small footprint. Very little impact on system performance.

And now there is Next-gen Endpoint Protection which takes that to a totally new level, with things like deep machine learning, forensic logging, SIEM aggregation, and threat intelligence data feeds.

You need nothing other than Defender and some common sense.  Win10 is very solid and third party anti-virus in 2017 is not necessary. Oh they'll spend millions to convince you it is but it's not. They are just defending a legacy business.

QFT

Windows 10 does not need third party anti virus/anti malware for normal daily use.

If you install cracked software/shady software there is nothing much that can help you except vm.

Norton and Mcafee suck.  They load your PC with a bunch of crap and slow it down.

I used AVG (paid version) for several years until it started hitting me with too many offers and extras.

I switched to Webroot a couple of years ago and have been very pleased.  It's small and never seems to interfere with my use.

Aside from finding out what causes the least trouble with you system it doesn't really matter.  Use something light on resources that you feel comfortable with and combine it with common sense and that's as good a posture as you can really have.  The vast majority of effective malicious code requires a good bit of the users cooperation to do anything serious.  See the common sense part.  That's the most effective anti-virus.

I think my Windows workstation and various portables have just had Traps installed during the last software push but that's not a traditional AV nor is it (at least I don't think it is) going to be a trivial matter for a home user to get and

I've also been following some internal write-ups from our security group reporting surprisingly regular incidents in which Win10 Enterprise 1703 with the full defender suite as the only security software is catching malicious packages and code.  Systems in the same environment that have a mix of baseline and control installs of 5 well known AV packages from enterprise vendors all missed them completely.  

No conclusive determination has been made but anecdotally that surprises the hell out of me.

Bad move. Defender doesn't seem to detect anything from my experience. Even Symantec and McAfee only partially detect fake antivirus and encryption scams. The new McAfee should be very effective at dynamically blocking anything but I haven't fully upgraded yet. It's supposed to look more at what the program is going to do than just looking for a signature. Anyways, Defender is not acceptable in my book. Viruses or "malware" (a term apparently invented for things antivirus simply could not detect for the last decade) are very sophisticated these days and you need a multilayer defense.

For home users that never do anything risky, like grandmas, maybe Defended is okay, but in all cases Bitdefender or Avast or Kapersky, or Avira, or anything else really, is better. Hopefully that will change in the future and Microsoft will get serious.

FWIW, i've used Avast for years.  But, i'm not happy with it, since its turned into bloatware.  

I've been looking for AV software that uses less system resources.

Eset's Nod32.

I'm on w10 so I just stick to defender and malwarebytes. I install the security updates whenever they're available and exercise some common sense. It's mostly a gaming rig though so 99% of my downloads are off of gaming clients. The few times I download something from a site they're going to be a legit site. No torrents and what not.