I would advise you to choose your PhD depending on the supervisor, no matter what is the subject.
Sorry, but I just don't agree with you on this one, choosing something based on what your boss is like is an extremely superficial way to decide your future life.
Doing something that you enjoy, are interested in and motivated by will be far more rewarding for 5 years even if you don't like the boss. 5 years will seem an awful lot longer if the work isn't enjoyable and doesn't interest or motivate you (No matter how nice the boss is).
And what of your Post PhD life? You'll have 30+ years of it. do you want to carry working in a field that you chose based on what the boss was like, or what interests you?
Sorry, but it seems you miss understood what I meant. Naturally, the decision to do a PhD has to be thought through carefully and it is much better to do something one likes. But, when a Student mentioned: "I want to study PhD, [...] which branch of organic chemistry is more attendable", I assumed he has already made his decision after much thinking and that he likes organic chemistry enough to make it his job.
At that point, I don't think working on any particular area of organic chemistry will make any difference to his motivation:
-Will he be happier if he works with phosphines rather than fluorine chemistry?
-Better with polymers than with natural product synthesis?
As a student who just graduated, he probably doesn't know much of the subtleties between different organic chemistry areas. And anyway, he will get to work on many of them during his career. So it doesn't really matter.
At that point, when someone has decided upon a PhD and which area (organic chemistry in this case), I keep thinking it is better to choose a PhD depending on the supervisor. Moreover, a good supervisor can help you make (or rarely destroy) your future career as an academic researcher. As his student, you benefit from your supervisor networking and influence, which could help you find a good postdoc afterwards... This is true regardless if you are good, or not so good, at doing science. It is the less glamorous part of science, where lab politics are important. I think it would be "an extremely superficial way" not to take it into account and leave it to chance.
BTW, nobody ever talks about that "dark" side of science (where it is not enough to be good, but need networking as well. where there are conflicts between professors and students are caught in the middle...) to students. The surprise comes later, when it is often too late.
The best way in my opinion is to find a topic you like, talk to the supervisors for each group, and then choose.
Agree. In this case, the topic chosen by a Student is organic chemistry. Then my answered followed: choose the supervisor, after talking to many of them.