Personally I use Vaude panniers. My rear pair are a model older than in the link, but I have a set of the newer front panniers. I like them better than Ortlieb. They are similarly waterproof but give rather easier access, imo. In particular I like having an external pocket for stuff I want to access quickly, or might need to lay my hands on when it's pouring with rain.
I've used the rear pair for years and many thousands of miles. They look a bit battered but are still waterproof.