Optimization (2D) - Box Collider vs Circle Collider

Hello,
I am almost done with developing a mobile game. Now it’s time for optimization.
There are a lot of places where I have used 2D Box Colliders but is it true that Circle Collider is more optimized?

Thank You

According to this post it is:

http://forum.unity3d.com/threads/capsule-vs-box-colliders.34254/

Fastest to slowest…

capsule
sphere
box

Personally, I don’t understand that. In my mind nothing should be faster than a simple overlapping rectangle (or cube) collision checking routine. But the test results definitely show box as being the slowest. Maybe it is something the graphics card itself can do these days.

Anyway, I doubt it would be worth the effort converting your entire game to use sphere colliders. Considering rectangles and cubes are the slowest method this aspect should be very fast in all cases. I think the biggest gains for collision checking would come from simply layering your objects and only allowing certain sets of objects to collide with other sets (enemies likely would not collide with other enemies or with powerups and so forth).

An answer specific to the 2D world can be found here (spoiler: circle is fastest):

Info on CapsuleCollider2D, however, is not included and I would be interested to see if it still outperforms box in the 2D engine (since it is now competing against a 4-corner box instead of an 8-corner box). No info on edgeRadius either (which, basically, on a box, turns a box into a capsule stretched two ways).