You asked to explain why I chose in the poll so here it goes.
I vote to use the fast travel because I think it will in the end be better. While the building of the minecart system may provide good RP I don't think it will. From what I've seen with the Dwarves, as soon as we start building we stop RPing as much. There is also the fact that the fast travel allows us to stay connected even better so we can still have lots of RP even with spread out cities. While the longer minecart journey could bring RP, you can just walk for that. The minecraft/fast travel system isn't really meant for that. It is so you can get somewhere faster. Then there is also the fact that if it lags or runs out of minecarts, or has a minecart left on the track, or a mob on the track, etc. it will end up being a hassle. In the end the fast travel will just be less problematic.
TL;DR
• I'm worried minecarts will actually lessen RP due to building taking time
• I'm worried about technical issues that will cause a hassle
• Fast travel helps keep the dwarven cities connected better due to its speed
Minecarts may be more "realisitc" but this server is to have fun above all (it is a game after all) and in the end I think the issues with minecarts will make it less fun.
EDIT:
Would it be possible to have both? That way those who like fast travel are good and those who want to use minecarts are happy as well.