Neither, YafRay renders an image using your processor, and does not render things in real time using OpenGL or DirectX. Your rendering errors with it before are probably because of the installation path (try installing it in C:\Yafray\ instead of C:\Program Files\Yafray\ by default), and remember to point where the YafRay.exe file is in Plug-In Preferences.
Also, it would be wise if you setup your own lights for YafRay too, like all standard renderers, the default light doesn't look too good...
AMD64 X2 3800+ | 1 GB Ram | NVIDIA GeForce 6800 128MB
MSVC++ .Net 2003 | Wings3D | CharacterFX | Gimp v2.0
Formerly NWC_Omega