I like the smaller party dynamic as it encourages you to make tough choices early on an gives you an incentive to replay with different characters and different party combinations.
How does party-size incentivize replaying the game? It is the number of companion choices you have in the game that can incentivize replaying the game, i.e., if you have a lot of companions available in the game where those companions are good substitutes for one another, such as was the case in the original BG games, then you can replay the game with different party makeups. So # of available companions helps replay (regardless of party-size). Party-size has no bearing on replay-value of a game.