I was bored so decided to render a simple scene on both BI and Cycles and see what the results would be. I tried to adjust the settings so that the scenes would match as well as possible, this includes the number of samples used to get about equal noise levels. Susane is pure matte, the cube is matte with 0.3 amount of sharp glossy, the sphere is pure sharp glossy and the plane is also pure default white matte. For the lighting there are two point lamps, another has light yellow and the other light blue tint.
First: 0 bounces (except reflection/glossy depth set to 2)
It’s amazing how the images look exactly alike.
Next: again 0 bounces but now with ambient occlusion
Still not much of a difference.
And then: 3 bounces
Difference is obvious, it’s impossible to get BI look like Cycles without real ray tracing for the bounces. Also while BI doesn’t really produce any noise it’s a lot less accurate. I only upped the number of diffuse samples in Cycles a bit, but there’s still some noise.
The result…? Well looks like BI can be a bit faster on some very basic scene this time, but anything more than that, you’ll probably want to use Cycles.
Build used for both BI and Cycles was mingw64 2.64