We used the cardboard box for many years but the tree would sometimes get dusty. The other problem with it was it being a real booger to maneuver out of the closet or attic and back into place after the holidays.
Of course, like a lot of people, we also stored our lights and decorations with the tree in the box. This is not ideal.
CoverMates 60" Christmas Tree Storage BagTreeKeeper Tree Storage Duffel, fits 6 to 9-Foot TreesSeasons Christmas Tree Rolling Storage Duffel
This year we decided to get a Christmas tree storage bag to keep the tree and its decorations in good condition. With the handle it's easier to move around and doesn't require 4 hands to get it into the top of the closet or the attic.