Should I disable Defender before installing a third-party AV?

[Vertigo]

Looking at installing some AV on my new Win10 system, probably going to give Avira a go (using Avast on Win7 at the moment).

Was wondering whether I should forcibly disable Windows Defender first or leave it running alongside Avira?

 

[Vertigo]

From what I've read Defender isn't much cop and the likes of Avast/Avira are better.

 

[Vertigo]

I have wondered whether it's really necessary or not. Providing you have a modicum of common sense when browsing/downloading/running stuff I presume AV can be unnecessary?