For a professional/work context, I think this is mostly a human (rather than tech. decision). What languages are the team comfortable in? Where is talent available etc.
If you're in services, then the general demands of the market/your niche are important factors.
For completely personal projects, if you're trying to learn language X, use X. If you're trying to build a project for some reason, then use the language you're most familiar with.
If you're in services, then the general demands of the market/your niche are important factors.
For completely personal projects, if you're trying to learn language X, use X. If you're trying to build a project for some reason, then use the language you're most familiar with.