I'm a fan of Schwartz, but there are problems with his scheme as well. You need the guys up front to run it. In a way he's like Ryan, in that he needs a specific type of player.
With Bradley, you are getting a guy who molds his scheme to fit players strengths. He made stars out of players drafted in the later rounds. Earl Thomas and Bruce Irvin, who was a part time player, were the only players drafted in the first round. Chancellor, Wright, Wagner and Sherman all picked after the first round.
And Bradley does a good job of mixing his schemes, on running downs he uses the 4-3 under, which looks like a 3-4 alignment. So it's stout against the run. Then on passing downs he goes to something that looks like a Wide-9, with two "Leo's", and they put lots of pressure on the QBs.
It's not complicated and allows players to just go out and play.