I have done some development in OpenGL in the C++ platform and was thinking about trying my hand at DirectX which I have heard is a bit more challenging than OpenGL. From what I have read, DirectX seems to be the more popular format so I was wanting to learn how to use it. Or should I spend my time developing the skills I have gained in OpenGL further? What are the major differences/advantages/disadvantages of each? What are your thoughts/suggestions?
PS - This is not a homework question - I was just interested in other people's thoughts on the debate. :)