An analytical way to look at this would be to compare the "net present value" of the future earnings from the two opportunities. Given that the startup has not

An analytical way to look at this would be to compare the "net present value" of the future earnings from the two opportunities. Given that the startup has not raised any funding or revenue yet, and I don't hear you saying anything about how exciting it is, I'd have to guess you have more upside in the training and learnings from getting proper software development mentorship.