Internet settings Configuration in Router or Windows OS ?

Hi,

I have a D-Link Wireless N ADsl2+ 4-Port Wi-Fi router and my PC (running Windows OS) is connected to the router via. LAN cable
Other devices like Laptop, Tablet, etc. are connected to router via. WiFi

My ISP IP address, subnet mark and DNS Server IP address are configured in Router
And also a different DNS Server IP address is configured in Window OS as well in (TCP/IPv4)

I have few basic questions
a) What is the difference between configuring internet settings in Router and internet settings in PC ?
b) If I configure internet settings both in Router and OS, then which internet settings applies or takes precedence ?

Thanks

Windows takes priority on the settings the only difference is if you set it in Windows you control the ip if you use the router you could get a different one each time by default most routers set themselves as DNS which is very slow settings to open DNS or Google is a lot faster

Thanks samuria for the reply :)