I'd agree with SKnake if what he meant was "dhcp".. seems to have come out wrong! :D (Not that DNS takes that much overhead either.)
I'd generally use a router-based DHCP server only when the following two criteria exist -
1. there is no local server at the branch to host DHCP
2. bandwidth is so low that a central DHCP server isn't efficient - OR - the connection is unreliable and central DHCP leases time out, leaving the workstation without an address. Of course, that's an indication of bigger problems.
Windows vs Linux - really depends on the comfort level of the admin and the configuration of your network. If you have Windows systems and admin experience, I'd stick with that, especially for AD/DNS integration. If you're comfortable with administering Linux, then that might be your choice. Using Linux, especially in a Windows/AD environment, requires a bit more savvy to configure properly.
It all really comes down to admin experience, resources, and requirements.