Right now REI is selling Ortlieb panniers and bags at a significant discount. Anywhere where people talk about bicycle touring, they’re talking about this sale. This is because, for touring, most people opt for the plasticized canvas bags because of their remarkable ability to keep things dry.
I have used these panniers for touring and for daily commuting in one of the rainiest places I’ve ever lived. And they work great.
Until they don’t.
The problem with waterproof bags on a bicycle, especially one that you’re living off of, is that they make it nearly impossible to dry things out. If you intend to tour you will encounter bad weather. Rain or snow will come in contact with some or all of your kit and once that’s happened you’ll wake up every morning and shove part of that kit into your panniers.
Those wet things will be in contact with whatever you’ve managed to keep dry and there’s no dry air moving through the bag to dry out any of it. Thereafter you’ll be stuck in this weird cycle of strapping things to your bags and racks in dry weather so that they’ll dry until the next low-pressure ridge moves in.
With the exception of the period of time I’ve used Ortliebs I’ve been using an aging set of Jandd bags since the late 1990s. I have rain covers for them, although sometimes I don’t even bother to carry them. For the things I want to keep dry (my sleeping bag and jacket for instance) I use a plastic bag as a liner. Otherwise, things get wet and then dry out as I ride.
If I had the money I’d likely replace my worn Jandds with some new Arkel bags. Same principle, but their mounting system is superior in every way.