Starling is definitely who investors would put their money on being long-term profitable and market leading.
Not sure I agree. Starling seem to be the less likely to collapse, but Monzos seen to me to be the more likely to be massively profitable. Building a large, passionate user base is far harder than monetising a large, passionate user base. If I were a VC, I would value Monzo far higher than Starling.
I hope I'm wrong, as I think that Monzo as a company are awful for consumers in the long term, but purely from an investors point of view, I'd back Monzo.