oolong-engine

I'm trying to pick between the Oolong and SIO2 iPhone game engines for my first game programming project. I have some Cocoa experience and many years of C++ including relatively low level 2D graphics and developing Quicktime plugins but only minor OpenGL exposure. Which engine would be easiest to learn and most productive for someone with my background and limited time? Both include the Bullet physics engine. I lean towards Oolong because of its C++ source and optimisation for the PowerVR graphics. However, the Lua interpreter and additional sound goodies in SIO2 are appealing. SIO2 also seems