Actually, the white hose is more for taste than any anti-bacterial reason. The material it's made of doesn't impart a "plastic" taste to the water.
As a long time RV'er, I would suggest the 25 foot length. So far, with a 26 foot 5th wheel, we've never needed our 10 ft. "backup" hose extension in many thousands of miles camping and I doubt if the backup would ever be needed on our C-dory.