I live on the third floor of an apartment, so I totally feel your pain about walking up and down stairs multiple times a day for potty breaks. However, Levi has made it perfectly clear to me that he wants nothing to do with pee pads. He'll use them in an emergency (I always keep one out for him), but if I am at home he goes to the door to go outside and potty. The stairs are rough, but I do prefer that he is outdoor-trained (and apparently he prefers that too).
Pad training might be easiest while he is a puppy and can't hold it for very long. However, I wouldn't completely give up on outdoor training if that is something you are interested in, especially since you are only on the second floor. I keep Levi on a regular potty schedule and it works out really well for us. I like that he gets a chance to go outside many times a day, and I like not coming home to soiled potty pads. The apartment thing is difficult, but once it became routine to walk downstairs, neither Levi nor I have minded it.