Which is better, a mattress with zipper or a mattress without zipper?

In terms of comfort, the mattress is not close to the body and the zipper doesn't matter.

As far as cleaning is concerned, if there is a zipper, the bedspread can be removed for cleaning, but if there is no zipper, it cannot be cleaned.

If he installed the zipper again and can't take it off for cleaning, it's just to show you the material inside.

Buying a mattress mainly depends on the external fabric and the internal material.