Irkutsk sells Asps at a 10% discount. For me, the reward of being a friend to the Alliance are just that I'm working with a type of government that seems to value freedom more. I'm not full on with the Alliance, my character is a freelancer, but he sympathizes with the Alliance. My pilot won't hesitate to work with the other powers to get benefits and ships from them, but if the chips were down my Commander would go fight with the Alliance.
The hardcore Alliance Edmund Mahon sympathizers are a tight knit community as well. The Alliance is the weakest of the 3 powers but they've made him the strongest Powerplay faction. So there's that too. A lot of it is just roleplay.