A few things that Donny’s constant and frequent change of arrangers show are that:
1. In a good players hand, any arranger can sound good. It is the player not the board.
2. Once you understand how to use arrangers, changing and learning a new OS to use on a gig is doable.
3. Mid and TOTL arrangers can do the job for most players TOTLs may have a few more features, but generally you can do the basic gigging arranger functions on both.
4. And when you get a review from Donny, you get it from a gigging musician in mind not just a home player. For most if not all of the arrangers he reviews, he actually sets it up and takes it on a gig before trading it. I think this is the best review you can get because you get a real-life application of the arranger. Not just an online demo )which does not tell you much), not just a 2 or 3 hour demo in a store and worst of all not just a review after turning on the keyboard and playing a style. The review you get from Donny is based on how most arranger players would use it after setting it up.

IMO the only reason why Donny changes arrangers )if there is even one) is probably the excitement of having something different at a given time and not that one arranger is better than the other.