When bandwidth matters, when you don't want to over or under provision, when you need multiple seats: if you make a project with a small team, Render is going to be quite expensive because of the cost of each seat while Railway offers unlimited seats for they paid plans. Just the whole pricing is different, I found myself more leaning into Railway when doing calculations.

Sorry, I wasn't saying you should split, I wanted to say that depending on what type of apps you are more leaning into one makes a bit more sense than the other. Render with their own CDN is quite good for frontend apps. In comparison, the whole config and auto scalling/provisioning of Railway makes it easier for backend app.

Of course you can do both with both of these services.