These are the most inexpensive unit in the game. They can capture buildings, and they're more mobile than Mechs. However, they are not nearly as mobile, nor as durable as Bikes, and they're fairly useless for offense, except against other Infantry.
Infantry are, however, advantageous when you have a lot of mountains to contend with. Mechs and Infantry are the only ground units that can traverse mountains that often create major choke points in maps. On maps with Fog of War, Infantry units can also see further from Mountains