....and the weight. Arkel stuff is amazingly heavy. The Ortlieb quick release is good and the Klick-Fix that clamps to the bars and only uses a single "one time use wire" is far better than the bracket that comes with the bag. The Ortlieb is simple, water proof, tough and light.
Glad you like your bags. Everyone buys things for different reasons. I bought Arkel because regardless of bag size (7L or 8.4 L), the Ortlieb bar bags, according to the manufacturer's site, all have a load rating of only 6.6 lbs - a little too anemic for my uses so I went for something with an internal metal / polymer framework. I want to be able to actually load the bag. Even Topeak's 5 L bag has a load rating of 11lbs. Arkel's 10 L bag will take more.
The other issue I had was that both the Arkel and the Ortlieb bags have external mesh pockets. The Ortlieb bag may be waterproof, but that doesn't help the contents of the external mesh pockets. So buying a raincover to protect the whole bag didn't really bother me. It was only about the price of the optional map case for the Ortlieb anyway. The map case is included in an Arkel bag.
I also noted that most problems with bar bags that came into the shop were related to either the mounting bracket breaking, or the support cable snapping.
So you bought what worked for you and I bought what worked for me.