Well, how do you begin to say one is better than the other? The Leica Duovid 8+12’s are only one of the finest pairs of binoculars on this or any other planet, with adjustable magnification and wide-angle view. Their aluminum and magnesium construction is utterly superb, as is their glass quality. Moreover, the Duovids are beautifully balanced and easy to hold.
Of course, for this you pay a premium: $1,400. But they’re a lifetime investment, not to mention one helluva heirloom.
On the face of it, the Swarovski EL 8.5×42’s are frankly just as good and essentially the same price. They’re also eight ounces lighter, the product of slightly different construction and the fact their magnification is fixed at a power of eightas opposed to the Duovid’s eight to 12 range. They’re also a slimmer design, something that may be a factor for extended hand-held viewing.
Generally, though, I gotta think the additional magnification afforded you by the Leicas makes them a superb choice for viewing distant objects and wildlife. The Swarovskis are slightly better “all-purpose” binocs, particularly when you’re both hiking and standing, due to their lighter weight and trimmer design.
If you can, try to use both, side by side, in a store. See what feels best and is most comfortable when stuck up against your face. But rest assured, you’ll not go wrong with either.