I have both of those, as well as a B-17, so I am interested in hearing your comparisons.
The only issue I have had with the Sella Anatomica is that the edge of the leather on mine is a bit sharp, and could benefit from being rounded off. I don't have the leather-crafting skills to do this without making a mess of it. My kid has had one for several years and it is still going strong.
As for adjustment, you use a 6mm hex wrench, which is convenient, because that slot should be about 6mm at its narrowest point, so you can measure it with your allen key.