It depends. On the games I love to play in, I love LOTS of interparty conflict. I like when a DM can construct a story by which all of the players have needs or interests in staying together, but they may have different opinions, ethos, & intentions for the quest. Getting a good love/hate relationship between the party is amazing, & I find that is usually better to do with larger groups of people, because with the more people, the more alliances form throughout the group, keeping it together better. If you just have four people, three people may not care if one or the other gets kicked out or killed, they might "need" the person for some reasons, but they may actualize that they can get by without them. If you have 6 or more people, the party lines aren't neccessarily so clearly stated, so when you require the entire party to help you, kicking one person out may mean you get kicked out from everyone else.