Hey I was wondering, you know how cause Aang a master airbender he has the capability to repulse armies with his Bending, what I wanna know is, is that kinda power limited to just airbenders or can all benders when they achieve the level of master repulse small armies?

each bending discipline is differnent and each one has its own strengths and weaknesses. Also, each bender is different in their styles. All that aside, air bending is a dynamic and counter style, meaning it is meant to defend from and defeat multiple opponents. I'd say a master earth bender could probably do this better because they're defensive, but much stronger and have more powerful and fatal moves. A firebender is more aggressive and would be able to take them out in an offensive defese kind of strategy. So the only one with any real trouble would be a water bender. Without a large source of water, or plants for a true master, it would be pretty difficult to defeat a great deal of opponents.
To answer simply:
Earth:better
Fire:more aggressive
Air:Well duh, u know this one
Water: a bit more challenging