I agree with #2 also. Both sides are equally at fault. The Jets and the Sharks both have moments where the audience naturally empathizes with the characters. One of the great things about West Side Story and Romeo and Juliet is that both stories draw the audience in, making them feel involved with characters on both sides of the conflict.
I agree with #2. I don't think there was any intention of anyone taking sides with either the Jets or the Sharks. The purpose of the gangs, as with the Montague/Capulet family feud, was to set up a conflict for no particular reason in order to elevate the tension between the main characters. Neither side, in either story, is "better" than the other.
I don't think there is any real difference between the two. I think this is supposed to be a Montagues and Capulets thing where both sides hate the other without any really good reason on either side. So I have trouble really taking sides in this.