There are actually only 2 cameras:
Standard (target and free are same setting inside it)
Physical (which also offers targeted use or not)
Physical is now the new default and there is no reason to use anything else, it's basically repackaged and improved Vray camera. I use it 100perc. of time, it's god-send, previously I had to use Vray camera (yes, with Corona, it workes :- ) .. ).
Some of the benefits: Vertical/Horizontal perspective correction and shifting, DOF settings and viewport preview (very nice), exposure and lots of more controls.