You pretty much will need to look at them side by side. Comparing brands is tricky with the range of quality the different brands have.
Different people's eyes are different. I learned that recently, shopping around. I compared a couple of models of Lieca and Swarovski, the Cabela's Euros, and Leopold golden rings, side by side. I would have compared the Zen Rays and Vortex as well if there had been some there to compare. To my eyes they were all excellent glass, with the Liecas and Swarovskis notably better. Between the two, the Swaro's were better in terms of clarity, field of view, ergonomics, etc... Are they superior to some of the other great glass? To my eyes, yes. To others? Maybe, maybe not.
I love my Leupold VX III rifle scope.
I love my Vortex spotting scope.
I love my Swarovski bins.
Most companies have some great glass. You just need to figure out the best for you that you can afford.