I have a stubben (well 8+ really) and love them, lots of options, great balance points, and happy horses. Even if you don’t have the most responsive rep, their guy at the office in Virginia communicates well and will do adjustments if you send it in.
My only experience with Arion is a current client who arrived with an Arion, we quickly discovered that the whole saddle was warped (no wonder her horse stopped cantering to the right), with the panels put on crocked. She got them to send a rep out, rep agreed, gave her a loner saddle (that didn’t fit). Her saddle came back, new panels same problem. They are still set on crocked even though they obviously took off the old panels and put on new ones.