Choosing PhD advisor between Professor X and an Assistant professor Y who was a PhD student of the professor X I got accepted in two different US schools for CS PhD programs. My prospective advisor/supervisor for the two schools are Professor X and Professor Y respectively. Professor Y was a PhD student of Professor X. Professor X has a lot of successful PhD students coming out of his lab and he is a heavyweight in the field. Professor Y is a tenure-track assistant professor but has really good recent A* publications. How should I approach this issue of choosing one of them?
(Moving from comment to answer)
This may not be true everywhere, but when faced with a similar decision I was told that the more established professor is more familiar with the department politics and how to get students graduated. Graduation should be a top priority, and if Professor X has a good track record of graduating students, that may be the best choice. Professor X also may have heavily influenced Professor Y's work, so it is unclear how Professor Y will work without Professor X's supervision.