I had to make this decision recently and my conclusion was if your goal is to build something that makes money, do it with what you know. Why? Because you can

I had to make this decision recently and my conclusion was if your goal is to build something that makes money, do it with what you know. Why? Because you can spend 100% of your time building instead of 50/50 learning/building (or worse). Projects with the goal of being a business should iterate and fail fast. If you win the app lottery and actually build something people will pay for, they won't want to wait for you to learn while you build it out. Someone else will do it with some "old" tech like ruby on rails and take your customers and revenue. Spend your time working on the business, not the tech. Developers think code is important but the reality is that it almost doesn't matter. You can build something successful with the worst tech decisions imaginable. I know it's hard to accept but it's true. I've personally witnessed an absolute frankenstein's monster app, made of a mish-mash of what are now considered the worst technologies, get sold for $30+ million and the founders retired to the Caribbean where the build a mansion and an upscale restaurant just for fun. I pity the people devs who have to inherit that, but the value wasn't in the tech and it almost never is.