The XD line is often compared to Glock. Some like it better then Glock. I have fired the 40 cal XD. I enjoy it.
The 357SIG is loud, and rounds for it are expensive. If you can find them that is. Good luck finding practice rounds.
That being said, the 357 SIG is a great performer in the self defense, and duty weapon category.
If I remember correctly, the recoil is rather "snappy"
The 357 sig fires a 9mm bullet. It's case is that of the .40cal. Think of it as a ++P9mm++. It can be compared to a .357, with a 125g HP load. (MANSTOPPER) it will put the hurt on drugged up pit bulls, and rabid bad guys.