On the new generation MKX you get a lot more over the Edge than in previous generations. We bought a 2008 Edge because we liked the styling better and couldn't justify the added cost. We were ready to buy a 2016 Edge but bought a 2016 MKX because we actually could justify the added cost. The seats are much more comfortable, it's much quieter, the Revel sound system is much better, embedded modem with mobile app, it had a unique color (luxe metallic) that we liked, the center console is cleaner and the interior materials are nicer. Add to that the longer warranty and the fact that Lincoln picks up the vehicle and leaves a loaner any time we need service (maintenance or warranty work) and we liked the MKX styling just a tad better and for us it was worth the upgrade.
Of course that all depends on what you value. Nothing wrong with the Edge.