I agree. All things being equal, picking one idea will get you somewhere. If all 4 things will make you happy working on them, and now you're just trying to f

I agree. All things being equal, picking one idea will get you somewhere. If all 4 things will make you happy working on them, and now you're just trying to figure out which is the "best" then just pick something so long as they meet your criteria for potentially successful businesses. And nothing says you can't validate more than one idea, but that is going to cut into your resources.