Potential downside of joining a rapidly growing department
My impression is that you are looking at the wrong factors here. For PhD training, department-level name recognition, or where in the usual rankings the department is placed, is both fairly irrelevant. The same can also be said about where students of the department usually go afterwards.

During your PhD, you will work first and foremost with exactly one advisor. You need to evaluate whether your advisor is strong and a good fit, and what her or his students usually do afterwards. The rest of the department is not irrelevant, but ultimately not nearly as important as your advisor.

Consequently, look at the professors in your field in the department who would likely end up your advisors. Would you think it would great for you to work with them? If yes, go there and don't mind whether the department is a few places down in some ranking, If no, don't go there even if they are "up and coming".