Without getting technical I'll just say, go with what they said above. Optics are pretty much the pound for pound deal. That is, you get what you pay for for the most part. The best glass cost money. You want the powers mentioned above and waterproof. At least that should be your goal. $$$ might determine something else in your particular case, but start with those givens. Terrain and what you use them for will fine tune your needs but the powers mentioned are generally the best.