I was going to say, How do you play with 4 people... you mean the recommended number? But then I thought that'd come off sounding snide. For more role-playing intensive games, I prefer around 4 (let's say 3-5) because you got the basics covered and people aren't competing for "screen time". My current group is 7 players and that complicates somethings; in a 4 hour session we're looking at maybe two combats.
That said, the larger parties definitely have an edge. You get some redundancy in your key positions, and it frees up other people for auxillary character types (like bards, frinstance) that might not be that much help in a conventional 4-person group. The last high level game I played (which means 10+ to me), we had a group like that. Two tanks, two fighter/casters, a dedicated blaster and a dedicated healer. At 14th level, we had to retreat from a CR 32 Pit Fiend. Everything else we rolled over. It was just a great dynamic.
With a 4 person (or smaller) group, everybody really needs to contribute. You can't have an empty shirt at the table.
That said, the larger parties definitely have an edge. You get some redundancy in your key positions, and it frees up other people for auxillary character types (like bards, frinstance) that might not be that much help in a conventional 4-person group. The last high level game I played (which means 10+ to me), we had a group like that. Two tanks, two fighter/casters, a dedicated blaster and a dedicated healer. At 14th level, we had to retreat from a CR 32 Pit Fiend. Everything else we rolled over. It was just a great dynamic.
With a 4 person (or smaller) group, everybody really needs to contribute. You can't have an empty shirt at the table.