synology has much more camera supported while qnap supports only very few
but, synology provides only 1 free license so you can connect it to 1 camera only. If you wanna connect more, you have to pay for each and costs ~400hkd each
qnap typically bundled with more licenses out of the box.
I tried both android apps it seems synology app gives more functions.
It's not 100% sure as I didnt own a qnap and just tried their demo.