I think a question is “what is the point of a backup computer?”The Aeris was much easier to read and more user friendly. I had the Cressi as a backup in case my Aeris failed. I never liked the user interface of the Cressi and that trip was the first time I used it. Hindsight is 20/20. Either way, I don’t see the point of having radically different algorithms. For me, it is Buhlmann ZH-L16c with GF or forget it. I realize that limits me. Back then it would have been more of a limitation
The answer depends on circumstances.
For a no stop dive there is usually little point. Maybe you can save the dive if your primary dies. If you are in the Galapagos then that is a big deal. Local shore dive, maybe not so important.
For proper deco dives you do want one, you want to be able to complete the dive without completely relying on a buddy, especially if gas choices etc are such that your computer plans might vary. In this case perhaps you care about the algorithm, but you’d plan for the conservative computer normally as you’d not plan to bend it so does it matter if they are the same?
TBH it sounds like you are proclaiming that ZHL16C/GF is the one true way.
Myself, I think that the algorithm is the least important feature. Having a difficult UI is a big deal. I discovered a couple of club members had their computers set in gauge mode a couple of years ago. I only realised when trying to show them how to plan the dive using the built in planner. All the other stuff like a nice screen or easy Bluetooth is more important to me than whether I know 80% of what they do for their calcs or whether I only know half of it.