When questions are asked about which bags to get, ortlieb tends to be the standard answer. Arkel has info on its website claiming that waterproof bags aren't as suitable for long distance touring as coated cordura (which not only Arkel uses but also companies like Jandd and Lone Peak) because of condensation and because it can be difficult to get water out once it gets in (which it is likely to do if you open and close them on a rainy day out in the middle of nowhere).

Here is the language from Arkel's website:

"Ask experience users of watertight panniers and they will tell you about battling condensation build up and that they use plastic bags inside the panniers to separate wet stuff from dry and to have some organization system that top load, one compartment bags don't provide. Having stuff separated inside make searching easier as these panniers are always of the one compartment top-loading type. Compartments are a precaution against the elements when digging through for something in a rainstorm and to avoid a possible water spill - in which case the open design watertight pannier becomes a watertight swimming pool with your stuff floating around inside."

Waterproof - Facts & Myths

Arkel is a competitor of Ortlieb's so you can discount this claim for that reason but it is a serious claim and one I've wondered about in the past.

I tend to think that waterproof bags are of little use on a long tour. Plastic bags help you organize your stuff and keep it dry. So why not get a tough cordura bag that doesn't keep water in if some gets out? I have trouble imagining a tour where you don't get water into your bags given that everything tends to start out a bit wet with the morning's condensation.

So is ortlieb the best thing to hit the touring world since sliced bread (or the peanut butter and jelly sandwich if you prefer, please no marmite, ) or is it overrated?