Converting to Unity Physics2D: Worth the effort?

I developed a game where I used an orthographic camera and a locked Z axis transform to create a 2D game -- although I sill used 3D object meshes for game objects so I could rotate and spin and such (i.e. coins, etc), the entire game play was done on the x/y 2D plane.

It all worked out well for me but it always bugged by that my game was doing more physics work and calculations than it really needed--although I could never prove that. It was just a feeling.

I don't currently have a performance problem but am always looking to optimize and optimize some more. Also, in newer versions of my game, I intend to add more game objects and utilize more rigid body action -- I currently only have about 10 game object that uses rigid body physics -- all others are static colliders.

My question: Would it be worth the effort, from a performance perspective, to convert my code over to use the new Unity 2D game system and physics? Meaning, was there some internal code optimization the Unity Engine was already doing for my "old" method with the orthographic camera and locked z axis where converting over to the new 2D system would basically be a wash and I would gain very little.

Thanks, Manny