The are a couple of benefits, receiving heal kits from other players, and by playing in guild challenges (where you can win recruiter points). Other than that there is also the chat bar where you can share tips and chit chat.
A guild challenge is where 2 guilds of equal standing play each other. More precisely 10 players from each are selected to try to beat each other with the guild with the most victories winning the event.
Each player selected can challenge up to two of the other guilds players (undefeated players only) to a match. With the points only being awarded to the challenging team player if he wins. Loses just use up a go.