Personally I would not disable it.
I don't know how much memory you have on your computer or what the CPU rating is however in any case I would not disable Windows Defender.
If you really don't want it to use up CPU processing I would just turn off the real time feature.
Go to the Window Ball - Type in Defender - Click on Windows Defender - Tools - Options - Reat Time Protection and un-check any of the three selections you want to.
The reason is I would not turn WD completely off, is because it is not necessary and since it is an integral part of Windows Security. By leaving Windows Defender on but turning off the "real time protection" you will still get their "definition" updates and can run a scheduled scans. Running a WD Quick Scan one a week can not hurt anything and runs fairly quickly.
My guess is that you will disable it anyway.