4). Larger party size means more variety. I'll give an example from Spiderweb games: The old "Exile" games had 6 players and the new "Avernum" HD remakes you can only have 4. And if you want the Tank, Archer, Healer, Wizard, Rogue and the archetype "Swings a Huge Sword" you cant. Maybe this was the thought behind the 6-man party back in the day? I know there were games with 4 members too (or more) but it 6 seems to have been the standard. This always feel like I'm missing something, like OK I guess I'll make the rogue the archer and the sword-and-board guy will have to heal. But it just not great, you know? Another byproduct of this is loot: you'll vendor so much shiny treasure and thats just sad.
One could argue it's exactly why a 4 members party is better, because it's more challenging. Not having the holy 6 present in your party goes for more strategic thinking as to which skills are more important than others for the next fight, making it more interesting during camp sessions for players like me who enjoyed a party of 2 in a DOS2 hardcore difficulty campaign.
