The Platinum has the burner in the back only. No heat from the bottom. The fan runs intermittently even when turned off. The RNB might do that too though. If you bake wedding cakes, I would not consider the Platinum unless you could try it out yourself, even if you have to drive somewhere to do it. There are reviews about how it bakes unevenly but some people say they bake in it. I would guess you are baking multiple layers at once which is different than baking one thing. If you can’t try it out, I would stick with the RNB like you already have experience with.

The RNB is a proven reliable design. I find the oven (once preheated) is exceptionally predictable and heats very evenly. I wouldn't give up on it without a good reason. And it sounds as if you feel similar and are very happy with your existing oven.

From what I have been told, the big advantage of the Platinum is that it preheats faster -- and that's admittedly something to be aware of with the RNB design. Is that something that would make a huge difference in your workflow? There is another thread here on Houzz that has a graph showing it takes at least 20min for a 30" RNB to preheat. And that's about in line with my own experience.

Are both of the ovens in the 48" range PowR models, or only one of them? That might solve your problem.

Personally, instead of changing from an RNB to a Platinum, in our recent kitchen remodel, we instead decided to supplement the RNB with some smaller Miele wall ovens (combination steam, and speed oven). That actually works even better for us. We can now pick between three different types of oven, depending on what it important for a particular dish.

I love the RNB for it's even heat, truly huge cavity, amazing broiler, and ease of keeping it clean. I like the Miele CSO for the fine grained humidity control and precise low-temperature settings. And I occasionally use the speed oven as an oven (rather than just microwave), when I find that two ovens aren't enough.