For me, the biggest hot buttons were application stability and developer support, which is where Unity and OTEE get top marks.
My target audience is 99% PC based, and all my experience is with Windows development, so I was pretty much in the same boat as you.
I'm not making an FPS, so I can't help with any specifics in that area, but I did dabble with Torque, DX Studio, Gamestudio, Anark, Blender's Game Engine and Deep Creator before moving to Unity.
