Depends on your needs.
The best Anti-virus (A/V) are the ones that are very aggressive and slows down your computer to a crawl. If you need that level of protection than sure, go with Norton, in your case.
Especially if you are in a company and seek maximum security and protection, where they are more important than having a smooth and fast computer experience. That is why school computers or work computers in many places, take ages to login in your account, and programs takes time to start.
If you use safe web practices, and that you know that if you open an image, and it asks you for admin privileges when you opened it, then you know something is wrong, and not give it, and you do backups of your stuff, and basically you follow these safe secure practices throughout (don't plugin anyone USB key inside, unless you trust that person and the content to be virus free). Then in this case, you don't need Norton, and Windows Defender will be sufficient.
Better the A/V, the more it will slow down your system. Simple as that. You can safely draw a nice correlation on that. Windows Defender won't detect hard to detect viruses, and because it is part of Windows 8, maybe, one day, some viruses will be able to by-pass detection, and Microsoft, might take a while before it gets fixed (several days or a week or two), but in the other hand, your computer acts like if you have no A/V installed, where everything is speedy and responsive.
For me Windows Defender is all I need. Under Windows 7 I used Microsoft Security Essential, and on my laptop, being slower, I disabled even that. The chances of getting a virus when visiting large company website, or school website are near 0%. And I know that Image.jpg.exe, isn't an image. I do, on occasion, enabled it to do a manual scan... finds nothing as always, 5 years of that
But again, it depends on you. It must be noted that my laptop doesn't contain any sensitive data. and things are backup daily. I could wipe the entire drive and re-install Windows, without worrying about a thing, or even get a USB key to get stuff back.