Route control is the ability to program turnout routes into the unit. It can be a handy feature. As an example, on our Chief, we've got routes programmed to get trains from staging onto the layout. Each route corresponds to a track number. If you want a train from track 7, just enter switch mode on the throttle, select 7, and push the "c" (closed) button to align the route. This would be a great feature for interlockings or any complex trackwork to move trains thru with a minimum of fuss.
As far as sound functions go, I think the Zephyr will do just fine.