I'd offer the following insights:
Both are good units.
Reasons to like Russound: Been doing it for awhile. None of the new product bugs that have, in past, plagued other products. New keypads look good; you can expand. Voltage triggering for slaves. (use diodes if you stack-more on that another day) Pre amp out as well as speaker out. Expandable to lotsa things. Governor on the back to keep little jimmy from blowing up speakers (hm. I've heard of that before). Easy enough so that moron who works for the builder can get it to work. Painless installs.
Reasons to like Niles: tuner included for radio fans (most folks are). Global control. Fixed out as well as pre out. Multiple keypads available per zone with extra parts.
In the words of a great baseball player, hit em where they're not. In other words, you'll make money selling a product that your competitors don't.