Good points all around. However, it may be important to prioritize features and your own riding habits.
From my view:
1. Panniers cannot fall off the bike while I'm riding. - Mounting system is most critical.
2. Panniers cannot spill contents or be difficult to repair in case of failure. - Minimize zippers.
3. Panniers should hold all the stuff I want. - Few big pockets are better than many little pockets
4. All panniers will leak, but some will leak so badly to ruin a day or week.
5. All can be somewhat repaired, but with some when they are repaired they will still be deficient.
Ortlieb and other top loaders with good waterproofing, and top loading would be my choice. I've seen them in action. Tom