This short video compares the time it takes to evacuate a couple of  Cactus Juice Large Chambers with a 6 CFM vacuum pump vs. a 3 CFM pump.  This is to demonstrate that the CFM rating on a pump is irrelevant for our purposes when using small vacuum hose.  Focus instead on the vacuum generated and save your money for quality since higher CFM does not make things go quicker or develop a deeper vacuum.