VR400 is the older version of VR600 , go check which chipsets they run for the ADSL/VDSL modem , a Broadcom chipset is always preferable . Also check the max link speed
of modem , some only do 24 MBs , which is cool if that's what your broadband package is , but if your package is faster you need the modem to be at least as fast as what your
max modem link speed could be.

Also check the link speeds on 2.4Ghz , 300 or 450 Mbps the only advantage of the 450 Mbps is it does 3 streams at 150 Mbps rather than 2 at 150 Mbps , even though both seem
to have 3 aerials , I have seen pics of some VR's having 2 aerials so make sure. Link speeds also depend on what you are connecting , the device has to be able to do 450 Mbps
also if you want to take advantage of the fastest link speed .

My Laptop has an Intel 6300 wireless card ( 3x3 ) which does 450 Mbps on both 2.4/5 Ghz so takes full advantage of 3 aerials and 3 streams , most only do 300 Mbps ( 2x2 ) . Its normally
written as 2x2 or 3x3 in the specs.

5 Ghz link speeds are also dependant on the device aswell , and 5 Ghz doesn't like walls and ceilings much , if you have line of sight 5 Ghz its fine but don't rely on it if you have thick walls as your link speeds won't be anything like what they say you can get.

LAN ports will also be 100Mbps or 1000Mbps ( Gigabit ) depends again on your equipment most new Laptops / Desktops have Gigabit as std .

Mr Dlink has shared the details,so there is only one more thing i want to say is that VR600 is full Gigabit ports while VR400 only has one Gigabit port.

thanks for the answers guys you really helped me.