What is the most convenient way to go from Frankfurt am Main Intl Airport to the center of Darmstadt on train?
RMV's website states there are couples way of doing this (S-Bahn, RE, etc.) However, other online materials suggests mutually contradictory things: the website of the conference I will go to in Darmstadt mentions the use of S-Bahn, while a previous city-dweller's web page states S-Bahn is time-consuming and recommends RE.
I am looking forward to see answers from people with first-hand experiences.