There isn't much to the powerline interface accessible via the Setup > PLC Settings menu. The single page shown in the screenshot below is all there is.
DHP-1320 Powerline settings
The main reason you'd pay the extra for the 1320 is its built-in HomePlug AV connectivity. In the HomePlug AV Adapter Roundup, I found a remarkable similarity among the products tested. The better products were able to maintain close to 40 Mbps of usable throughput in test locations spaced across my home.
I'm happy to report that the 1320's powerline portion performed similarly. I ran tests in the same three locations used in the round-up and was rewarded with steady throughput above 40 Mbps in all locations.
DHP-1320 Powerline three-location performance - downlink
The best case same-outlet throughput was even higher than I measured in the roundup, coming in at 51 Mbps for both up and downlink.
DHP-1320 Powerline three-location performance - uplink
Running more than one simultaneous stream raised the total throughput a bit. Running simultaneous up and downlink tests yielded a total of 64 Mbps.
DHP-1320 Powerline three-location performance - up and downlink
You need a high-bandwidth powerline connection in order to get the full benefit from extending an 802.11n wireless network via a powerline-connected AP. An extension AP may have a higher-bandwidth connection to a wireless client because it's now closer. But if that AP then has to connect via a 10 Mbps pipe back to the main router, you might as well use a wireless repeater.
It looks like the DHP-1320 has a nice combination of features—100 Mbps wire-speed routing, 802.11n wireless with good low-signal performance and HomePlug AV powerline bandwidth capable of delivering reliable 40 Mbps bandwidth.
So when I pair it up with the D-Link DHP-W306AV PowerLine AV Wireless N Extender I also got in for review shortly, I expect to find the best solution yet for building a fast, reliable multi AP wireless network without having to string Ethernet cable.
If you've been thinking of trying powerline networking again, the DHP-1320 would make a good place to start. You'll get a nice 2.4 GHz N router with HomePlug AV built in for a price as low as $65 (current prices from TigerDirect and CircuitCity at Amazon )!