All the comments about light gathering and scope quality are +1. Let me add that one's got to be able to see the aiming point.
I am not yet sold on battery powered optics, but the new generation of high quality dots are pretty proven. If you don't mind a battery on your rifle.
The Trijicon post w/ the glow tip seems appealing and its "no battery'. I don't own one, but like the concept.
Before tritium and high tech dots, fat chunky reticles were applied in low light. The Leupold 6x42 is often thought of as a low light scope and often appears w/ a "medium" duplex, likely for that reason.
Taking that idea a step further, the big blocky German #1, not popular in the US with most folks, can really be seen in dim light. I've got a couple on various riflles and can attest to how easily seen the aiming point appears. I once read somewhere that the Germans developed the #1 for that reason, but can't really say for sure. Leupold can put a#1 in most of their scopes.
Last, any scope on a "package deal" is sold to a price point,and may suffice, but can likely be easliy exceeded in quality. The old addage of getting what you pay for applies double in optics.