Many years ago (10+), I looked at both the Leica's and Swarovski's at several stores. I came away with the opinion that the Leica's were just a bit sharper. Not much difference IMO, and different eyes and different setting may tip the decision the other way. I ordered the Leica 10x42 BN's. What they sent me were the 12x50 BN's. I decided to keep them, and I really like them. Last year, the left barrel would no longer focus for me. I sent them in and from what I can tell, they didn't rebuild them, but sent me a brand new binoc. I like Monty's suggestion, and I'll add, look towards a low sun. That's tough duty for any optics and may point clearly to your winner.
10+ years in optic design is a long time, so take my experience FWIW...old. Good luck in the search.