All kinds of nylon filament thread are hygroscopic. This means that they will easily absorb water.
You’ll be surprised to know that nylon filaments are able to absorb 10% of its water density in a mere twenty-four hours. To avoid this, keep the filaments in a bag or container that is airtight and make sure you put a desiccant.
Nylon 12 absorbs only half of what the nylon 6 does so with that, we can say that you’ll have a better printing experience with nylon 12 as you won’t have any problems with too much moisture in the filaments.
Nylon prints that have absorbed water prior to printing will have finishes that are not desirable. You may even experience them popping in your extruder. If your nylon filament is sure to be dry, it will have a smooth and nice sheen. To ensure that you will have only the best quality prints, dry your filaments first before printing with them.