Test ride all plus other bikes and get what you like best. I'll say the following about each though:
Kona: Never ridden one, but I've heard good things. Assuming you like the ride of all of them, I'd probably pick this.
Giant: I hate Sram trigger shifters, and I know I'm not the only one who does. I'd pass on it for that alone, though I don't know how you feel about them.
Trek: They feel different from other hybrids, and it's kind of hard to say why. I am not that impressed with how they feel, but things like Trek's warranty and rack mounts on the fork really make me want to like them.