Decide if you want the waterproof panniers or not. And decide if lots of external small pockets are important to you. Once you make these decisions, that makes your decision a lot easier as the list of options gets much shorter.

I have Ortlieb classic rollers, front and rear. I also have some nylon ones with external pockets. If I was going somewhere that would be dry most of the time, I would leave the waterproof Ortliebs at home. But this summer where I go it may rain more days than not, I plan to use the Ortliebs. I also have the waterproof duffle that goes on top of the rear rack but I will also carry a mesh duffle to use instead for dry days if I have things that I want to dry out instead of steam in the heat in an airtight container.