For me with Martinez, purple patch or not, he has shown he is an important part of our passing out the back game. Thay being said we seem to have improved overall as a team in this sense with the players knowing which positions to move into for the next pass etc, so the question for me is can Leno pass out the back to a similar high level? Is the team's comfort in passing out the back as a result of Emi's inclusion in the team or is Emi's distribution looking this good as a result of our improved understanding of Arteta's passing instructions by the team?
The things Emi definitely seems to have in his locker, form or not, is his height allowing him better control of his box and getting to high balls as well as his distribution both long and short. We just have to see if he's able to keep this up.
Leno is a great shot stopper as well as a quality keeper overall and has been consistent over many years. Although there are question marks over how he returns from injury as well as whether he can distribute and command high balls to a similar level as Emi, he deserves a chance at some point this season to prove whether he can fit into the way we want to play. However this can't be immediately as Emi has earned the right to be No 1 for the start of the season.
At the moment I'm leaning towards Emi because of his physical attributes as well as his ability on the ball however there isn't much in it. It'll be a tough decision to make in the end but like some of the others have said, I don't think it's something we can, or should, decide this soon.