I feel your pain. I live on a third-floor apartment.
That being said, I do prefer that Levi is outdoor trained and I give him every opportunity to go outside. Even at 3 years old, he is on a very consistent, predictable potty schedule. I think this helped him learn to "tell" me when he has to go outside. He'll sit by the door when he needs to go out, or if it is an emergency, he will cry at my feet.
He will use the potty pads if he is home alone, but definitely prefers to go outside.