I chose Arkel for the extreme durability and the functionality of it (I like pockets and the rack mounting is excellent) however I would have no qualms whatsoever going for Ortleib. They make some fine panneirs that lose all the pockets but are fully waterproof and have a pretty nice rack attachment system. Those are the two modern brands I would trust for panniers. Certainly there are other smaller makers doing some cool stuff but that can usually be more expensive.

My Arkels cost a lot of money but the usage I have gotten out of them has been more than sufficient and I know I will have those panniers 20 years down the line and they will still be excellent. I like to buy high quality gear that will last and last rather than the cheaper stuff and keep re-buying it. I also like the really nice stuff because I know I could resell it and come out OK.