/roll is a fine system for casual guilds that don't really care who gets what, but if the guild wants to do progression seriously, there's too much risk that important items go to people who aren't going to do a whole lot with it.
EPGP is a great system, as it generally rewards people who are contributing, but again, someone who isn't that good may just save up EP.
The best system for a progression guild is and always be loot council. However, it is completely dependent on having non-biased, trustworthy council members. If your guild's officers can be trusted and are rational, smart people, this system is the best. In a guild the GM wants to gear up the girl trying to get in her pants, however, it's not going to work so well.
TL;DR - Every loot system is based on the presumption that nobody can be trusted, except for loot council. If you do trust them, loot council is the best.