First off, welcome to the game.
Secondly, you should join us for some AA Minis Play-By-Forum!
You win the game by taking the objective, and there is no better force than soldiers for doing that.
Think of it this way. A Sherman is 21 points. You can get 7 Mausers for that cost. In a straight match up, the Mausers will complete the mission (hold the objective on turn 7) more easily than the Sherman! It just doesn't have enough time to (aka assaults) to take out all of the Infantry.
Now imagine you played a few tanks and anti-tank guns. How much extra time you have to get your infantry to the objective while the armour slugs it out. Ideally you've got more Infantry on the objective at 7 than your opponent. If he doesn't have any Infantry to contest the objective then that expensuve armour has to come right next to your infantry. Then that speed 1 works just fine!