zipper choice?

[ArisaemaDracontium]

It seems that most people are choosing waterproof zippers, I am just curious why that is? My wife is making me a frame bag for my new Beargrease and typically we have been using 'sports' zippers from the fabric store because they are easier to pull than the waterproof ones and readily available at the local fabric store. Since the rest of the bag will be Cordura and not waterproof, any other reason to choose the waterproof zippers besides looks?

[12wheels]

Water-resistant zippers are easier to work with and offer extra protection against the elements.  They make sense if you have access to them and the rest of the bag is waterproof.  Regular zippers with a flap covering the track are as effective but require a few extra steps in manufacturing.  If you're not going to be spending long hours riding in the rain, waterproof fabric and water-resistant zippers or flaps aren't needed.   Carry a few small trash bags with you as insurance in case things turn ugly.