So if you're wondering which game to play, keep this in mind. A.V.A has 10x better graphics than Soldier Front does. Both do have good gameplay and teamwork involved, however in my opinion, I think Soldier Front would take it in gameplay. I mean, SF has so little but so much to offer.
I for one have only played A.V.A 3 times, but I can see it's major difference between SF.
But seeing how you can, why not try both and see which one you like? ^_^