You're fine with either. I chose MM's Pt900 Ir because I drink the KoolAid that his livelihood depends on choosing the best PT mix for his work. Also, I was asking the setter to put an inclusion right under the prong, so I wanted something that's a bit more malleable than Pt950 Ru. That said, people don't complain about Tiffany Pt950 Ru or they would have changed it.
I don't think it matters, either. I have both and really can't tell the difference. Victor uses 90/10 in case you want to balance out the vendor preferences.
I really like how the prongs look, very classy. I think the stones look much more balanced on your finger than the bezels do. I know this might be a lot of prongs, but what about 6 tiny claw prongs for the diamond since it will sit higher & you've admitted being rough on your rings. LOL Maybe 6 prongs on each sapphire would be too much but if the prongs are delicate & finely done, it might look ok. Otherwise, just leave them all with 4 prongs. I like it.
I always thought the 950 Ru was the stronger of the 2. Thats what I've had all my rings made with. I usually bezel everything so maybe it doesn't matter. I think both mixes are used very often without concern.