For low light hunting 50mm objective is better than 40mm. Medium to heavy duplex reticle is better than fine crosshairs. European glass is probably consistantly the best, but you pay for it.
One of the main reasons they make $1,000 + scopes is because people are chasing the best for low light & clarity. Hard to justify the difference in price between a Tasco & Swarovski during daylight hours, but the high end European scopes will give you give you an extra 10-15 minutes hunting time at dawn & dusk.