How much faster 2D physics is, compared to the 3D one?
The gameplay of the game that I am currently working on is happening in 2D (one of the axis is constrained). I am considering of switching to 2D physics and want to find out how much effective it could be, mainly in terms of performance.
Run a quick test, as it probably depends upon you’re games use of physics, e.g. a top down or side scrolling style game.
Yes I will downloading my copy of 4.3 
Probably there is already some data available on the 2D vs 3D performance. And I am sure there could be some things that I may not see only doing tests on my own.