Persolanny I think your criteria to chose a Ls is a bit misguided. Most important thing you should be looking would be for a Linkshell which ould be active at the same times as yourself, with people that you feel confortable playing with and are able to help each other.
I can tell you that having vent is not that important, although we have one ourselves this is mostly used during events, on a normal day it will probably only have a couple people or be empty as people seem to prefer to comunicate over the game.