I dunno, both are important, but I think between the two, you need to finish the level quicker than not. It seems like even a change in the minute affects the score pretty negatively. Once you get up to x8 and x9 it's all pretty good. I think my 4.4 million score had x10, my 4.3 before that had x8 - but I finished about a minute quicker.
--
Knowledge is the eye of desire and can become the pilot of the soul.