I like the 8-party behests, personally. Behests are pretty much beat-em-ups. You go to a group of mobs, kick their butts, and get money and experience. But if strategy needs to be involved in parties, then smaller parties will be easier to work with, unless you're in ventrillo with a full party. In fact, I've been in a league of alliances with 100+ other people on AION, using ventrillo as a domain so that the Brigadier Generals (guild leaders in the league/faction leaders) can give orders effectively. It depends on how hard a large party is willing to work towards organization.