Have I been mislead by a Microsoft support member here in Sydney who asked me why I was using Avast when Windows Defender was quite adequate? He also said that Avast might be preventing some automatic upgrades of Windows 10.
Depends on your browsing habits and the layered approach you’ve taken for your security, for some people Defender is quite adequate combined with other products and others need a solution that covers a broader area within one single product.
The only updates that would be prevented might be signatures for Defender as it would be disabled when any third party AV was installed.