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 Bag
TreeKeeper Tree Storage Duffel, fits 6 to 9-Foot Trees
Seasons 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.