The one reason I'll stay with Railway over Fly is that Fly is not as flexible with diverging CPU/memory requirements. I have a few apps that are memory heavy but don't need a lot of CPU. My Railway bill reflects that, with almost no CPU charge. And I don't have to think about upgrading or downgrading my instance size at all.
If they manage to implement that, they'd be the ideal replacement.
If they manage to implement that, they'd be the ideal replacement.