Free: Contests & Raffles.
I had the old SLC 15x56 until they were stolen a little over a year ago, I loved those binos. Swarovski shipped me a new pair overnight by fedex and the new hd SLC is even better, noticeably better. I highly recommend them, but if you are not used to high power binoculars you would be better off with a lower power than 15x. I can't speak about Vortex, I've never compared them.
I ran the slc non hd's for years and they were great. Decided to upgrade to the slc hd's and don't think I needed to, can't see any difference.
minimal but the hd's are a bit less bulky. I'm sure you can find the exact specs
Where'd you end up buying from? The cabelas here in Yak doesn't stock them (store sucks) so I haven't had a chance to do any side by side comparisons