Should I use OpenGl or direct3D?

[Joaquinamadeo]

Which one relies less on cpu and more on GPU? These are my following specs.
G3258, gtx 670ftw, 8gb ram, and i'm using latest developed dolphin version.

[JMC47]

OpenGL will be better in most cases, but in a game that relies heavily on certain EFB stuff, D3D will sometimes be faster.