I think bags are better than containers for the freezer, mainly because they take up less space, but also you can squeeze excess air out. I didn't have a preference for a certain brand of bag, all the ones I tried were easy to pour milk into from the bottle/ container you pumped into. If you use avent bottles you can pump directly into them and keep them in the fridge, You need the sealing disc to put into the lid rather than the teat. Then you can just pour it into a different bottle before you warm it for feeding. Or you can buy the avent containers, but I felt they were a bit of a waste of money.