Hardly worth comparing Chris. Although I agree with your assessment of their quality, the comparison is pointless. Fleetwood Mac used two or three guitars over a minimalistic rhythm section to achieve their sound. No one can accuse Ginger Baker and Jack Bruce of being minimalists!
The bands had completely different musical ambitions and focus. I'd say that about all they had in common musically, was that they were British blues bands of the sixties. Can you imagine Cream doing "Albatross" or "Man of the World"?