I doubt anyone has serious time behind the Leica HD-B's yet, a few are starting to trickle in but aside for some selected for pre-issue testing (which I don't put much stock in anyway, too much "play with our toy for free then go say nice things about it" going on) there isn't much info out there about the HD-B's yet. I checked them out at the shot show and was impressed in the handling and features, but again you can't put much faith in anything that's a demo at the shot show, you know it's been gone over with a fine tooth comb and a conference center indoors isn't the place to test optics anyway.
There's a foreign site where someone appears to have done detailed light transmission testing with two of your listed, the Victory and the Swarovski, and at least in light transmission the Swarovski won pretty handily. In fact the 10x range spanked even the 8x Victory RF. You can use a translator on it but really all you need to do is scroll down to the charts. The 8x leica geovid HD's barely hit 85%, the Victory RF 8x is 88-90%, and I'd say the swarvoski range 8-10x is close to 93-95%
This shouldn't really be a surprise, the swarovski's are the latest to be released and every iteration by these manufacturers seems to tip the scales just a bit compared to the competition. My guess is the Leica geovid HD-B's will do the same, and gain when Zeiss comes out with a new model down the road etc. etc.
http://www.houseofoutdoor.com/testr...skiELRange8xen10x42enZeiss8x45RFdec2011-1.pdf
One thing I wonder is it appears all the manufacturers are now using a new type of prism to gain most of this jump in light transmission, and it's a significant jump, I'm wondering what if any trade offs are there to get this extra light transmission in the way of image resolution, glare, ranging accuracy, etc. The Victory HT currently being toted as the brightest binoculars out there by Zeiss is claiming 95% transmission and by the site above his tests would appear to confirm it (or darn close to it), which is if you again believe the charts ~5% better than the Victory FL or Conquest can do, and close to 10% better than the leica ultravid HD all in the same power. Tests don't seem biased, in that none of them appear to repeatedly favor one brand.
You really can't go wrong with any of them, and at this level it's splitting hairs, you are probably better off choosing on ergonomics and features than optics alone. That said in my experience swarovski has the best no questions asked customer service of the three, but the other guys are going to take care of you as well. One issue might be that the Zeiss and Leica's will range down to about 10 yards, but the Swarovski is 33 yards perhaps an issue if you bowhunt. It also sounds like the new Leica will not do angle compensation under 100 yards, so it's not going to give the angle feature for bowhunters. All of them now have ballistic information systems built into them, however the Zeiss cannot compensate for up/down angle shots as the Swarvoski and new Leica will, in high relief terrain that's a huge feature (if it's accurate). The Leica appears it will have a significantly wider field of view compared to either the swarovski or Zeiss, about 10% more (330ft for the zeiss/swarovski 10x) and 374ft for the 10x leica.
I'm waiting to see how the HD-B's do on the market after this hunting season, the other rule I like to live by is don't buy any new product the first 6 months it's on the market (or it's first hunting season), let other people do the beta testing for you. Too many high dollar products hit the market and have issues, it's just a consequence of having hundreds if not thousands of people putting the product through it's paces once it hits the market that shows flaws that don't show up in limited pre-release testing.
As to the power, it really depends on you and your hunting, lower power is easier to hold steady and it gathers more light (with the same objective). Most guys won't buy 7-8x binoculars if 10-12x are available because it's an ego thing, bigger must be better, it's why guys are shooting antelope with 300 win mags and mule deer with 338 lapuas. If your hunting frequently allows you to rest the binoculars on something while glassing then the extra power might be worth it. I've had more than one guy reluctantly admit after using my 8x42's that they could resolve more detail than their 10-12x binoculars because they could hold them steadier.
