If the Sig feels better in your hand, I'd go that route. If you get the XD you'll always wish you had the Sig, too. Maybe you'll end up with both, but my advise is to get whichever feels more natural in your hand, and you said that's the Sig.
I've shot both and I'd say the Sig has a nicer trigger, but I like the grip safety, chamber indicator and lighter weight of the XD too. Both are great guns with good reliability records, and neither would be a bad choice. Again, get the one that feels better in your hand.