I think right BVH is better as B and C bound the primitives more tightly. You will need to run a test for intersection with D and F for each ray hitting B and a test for intersection with F and G for each ray hitting C.
You will need to run more tests for the first partition as all the rays hitting B an C will need to be tested, even those passing through the whitespace in B and C. With the tighter bounding boxes in partition 2, you will need to run fewer tests overall.
I think right BVH is better as B and C bound the primitives more tightly. You will need to run a test for intersection with D and F for each ray hitting B and a test for intersection with F and G for each ray hitting C.
You will need to run more tests for the first partition as all the rays hitting B an C will need to be tested, even those passing through the whitespace in B and C. With the tighter bounding boxes in partition 2, you will need to run fewer tests overall.