Should I pursue a good advisor-match or institutional prestige / pedigree? I'm in a conundrum! Which one should I choose for my PhD in life sciences in the US: a great-fit advisor in a mediocre institution VS an OK (or potentially ill-fit) advisor in a prestigious institution? 

I know it sounds obvious ---go with the good match (I also want this at heart)! BUT I also know that pedigree matters A LOT when applying for grants / conferences / publishing during and after PhD (unless you're back into a stellar institution for your post-doc* I guess?). 

(*) I assume I can find a good-match advisor in my post-doc in a stellar institution, despite the mediocre PhD institution label on my CV, if I publish a couple high-impact papers with this good-match PhD advisor.

Background: I already have a master's from a super high-prestige institution in the US and I have a very specific research interest and goal** (so, I might be less malleable than a lot of fresh out-of-undergrads who are also applying for these PhD positions). My goal is to become a professor (I think it's an awesome job, you get paid for following your passion!).

(**) the well-match advisor is also on board and excited about this goal in particular, my vision in general. We chat multiple times on this topic; we really click well with her! Also people in her lab seem very happy and she is VERY passionate in her research, which is good because I am too!

Thanks for your help and insights in advance!
There are some undefined terms here, so it is hard to give a definite answer: mediocre, for example. But there is some general guidance. 

What do you want to shoot for as a career? Do you want to do research in an R1 at the expense of all else? And a top-name R1 at that? Nice goal, but few achieve it. But studying at a top institution gives you some background for that. Or do you want to teach and otherwise do some good? 

There is very little worse in a doctoral program than having a bad advisor. But bad means someone who isn't very interested in your work or is hostile to you or your ideas in some ways. Browsing around this site gives many examples of the horrors. 

Having a high prestige advisor, from a high prestige institute (or not) will be a help for you in getting your first job, but it will decline after that quite rapidly and you will stand on your own. On the other hand, if the advisor, from wherever is connected to many others in the field, you can enter into many fruitful collaborative arrangements through the advisor and these will serve you throughout your career. 

But the high prestige advisor may be too busy to give you the help you need, or, since you have your own ideas already, too disinterested to help you when you really need it. 

But, it would be good to think long term about what you want, and the best choice will depend fundamentally on that, not the other factors you mention.