Not to be a Vortex proselytizer, but I love love love my Crossfire 12x50s and have had them for two years now. The optics are great (very sharp!), the construction is solid, and the lifetime warranty brings great peace of mind. I've used them to spot countless planes and birds, as well as to make my first confirmed observations of Uranus and Neptune, not to mention resolving a tiny globe on Jupiter and daytime observations of Venus and Jupiter. Can't say enough good things about them. I also love the fact that they have an IPD wide enough to accommodate my giant head, which very few binoculars actually do.
I also had the chance to try the Vortex Vulture 15x56 back when I was debating on upgrading for the higher magnification, and to my eyes, they weren't quite as sharp. The view was good, yes, but it lacked that crystal clear clarity I get from the Crossfires. Ultimately, what tipped me against them was the fact that the IPD was just a hair too narrow for me to look through comfortably. It's worth keeping in mind how these factors can make such a difference in usability; I'd have been able to overlook the decrease in contrast in the Vultures if the IPD had been large enough, but at 74mm in the Vultures, it was constricted, while at 76mm in the Crossfires, I never feel like there's not enough room for my eyes.
Someday, I'd like the chance to try the discontinued 20x56 Kaibabs or the current 18x56s, simply because they also extend to 76mm IPD. However, until then, I'm sticking with my 12x50s. Love them!