The producer of Splatoon, Hisashi Nogami, recently spoke about the choice to make battles 4 vs. 4 in the Wii U title. Speaking with Nintendo Dream, Nogami indicated that problems arose when considering 3 vs. 3 or 5 vs. 5 due to the potential impact on a team when it lost a player. According to Nogami, 4 vs. 4 makes the loss of a player just enough to create an unfavorable situation for a team, similar to a power play in ice hockey.
The full quote is as follows:
“It’s not like we couldn’t have made 3 vs. 3 battles, but if just one player is splatted, the balance changes drastically and the enemy team can make a push in one go. On the other hand, when we tried increasing the number of players, the effect of splatting one person was small. However, when we tried 4 vs. 4, just splatting one player got the other team into a quite unfavorable situation. It is like a power play in ice hockey.” — Hisashi Nogami
Source: Nintendo Dream (via Nintendo Everything)