I second this site - it's research-based and takes an objective view at several factors including how solvable a problem is, how many people are already working

I second this site - it's research-based and takes an objective view at several factors including how solvable a problem is, how many people are already working on it, etc. The podcast they host has some great interviews as well. Marta - I find myself on a similar path and I wish you the best of luck going forward!