Some people order a chicken Caesar salad on the side when they go out to a restaurant. Others order a chicken Caesar salad as their main course. Nobody would order the salad for both a side and an entree. That would not make sense. Two chicken Caesar salads would not compliment each other at all. The second salad would be redundant.
This is essentially the situation for the Jets at safety where New York starts Eric Smith and Jim Leonhard. They are both very good against the run but not athletic enough to be that good against the pass. Since Smith has taken over a spot in the starting lineup, Leonhard has been pretty quiet. Smith does what Leonhard used to do.
I think Leonhard is a better player. He is more of a playmaker and better in coverage. You can live with him as your number two cover safety. Smith is really a nickel linebacker. He plays the pass better than the average linebacker and the run better than the average safety. A tweener like him can have a lot of success as a situational player. When he becomes a full time starter, he ends up allowing more yardage in coverage than any safety in the league as he has to this point.
Both Leonhard and Smith are heady players. This matters. So does athletic ability, though. I think the best safety play the Jets got in the Rex Ryan era was last year when both were out of the lineup. Coverted cornerback Dwight Lowery and versatile Brodney Pool did great work in their place. Pool became a playmaker near the line of scrimmage. Lowery was a good pass defender, which is more critical than run defense from the safety spot given the current trends of athletic tight ends and high octane passing games. I think the best safety duo the Jets could put out there today would be Kyle Wilson at free safety and Pool at strong safety. Neither guy is a starter, though.