With the exception of flashlights, (in particular the newer LED weapon lights), I have never seen a battery powered anything that works as well as the same thing in 110V. They just don't have the power. Drills, vacuum cleaners, ect.
Using a "Dustbuster" type vacuum for a quickie cleanup for something easy is fine. But for giving the floors of your vehicle a good, deep vacuum cleaning, you cannot match 110 volt power with a high amperage motor.
I second the Dyson V6, I have been using one for over a year now with my Summit and it works great. I especially like the soft bristle brush on the leather.