This is an interesting topic.
I've always noticed a person's scent disregard of gender. Ironically, before I started dating my boyfriend I didn't really like his smell, it was a bit too sweet. But, now I love it. Sometimes I'll swear I smelled it and miss him. I also have a pack of incense he gave me, which also reminds me of him.
Being bisexual I've also dated women. Their scents are only a tad bit different if there's even a difference at all. They wear so MUCH perfume though! I don't usually mind, perfume smells nice. But, you really want to know the scent of your partner, something you can really link back to being theirs.
I've also noticed that some of my exs' smelled awful. One was sickly sweet, another was just gross. I of course realized I wasn't attracted to these men squat and had very little in common with them.
I think scent/pheromones play a huge role in the science of attraction. I sort of want more studies to be performed in regard to sexual preference based on scent. Will a homosexual woman find the scent of other woman more attractive than men in a blind study? I'd be really interesting to find out.