What is the best platinum alloy to use?

[L1quidforce]

I've read several of the articles about platinum and platinum vs gold. But a lot seem to contradict each other, one says platinum iridium is the whitest but very soft and shouldn't be sold, another says platinum ruthenium is almost impossible to find. What about platinum cobalt? What is the most common alloy that jewellers use?

I'm getting a custom ring made that is fairly intricate, is there an alloy that I should ensure my jeweller avoids/uses?

Thanks