Power is meaningless. Ignore a telescope that claims lots of power or magnification. Most observers rarely use high magnification because the atmosphere is never steady enough from your backyard. You'll find that most observing magnification with a beginner scope is from 50-125 power. This is more than enough to show craters on the moon, the rings of saturn, and moons of jupiter.
Aperture is important.
Aperture refers to the diameter of the lens or mirror collecting the light. Of course there is a tradeoff. Once you get bigger than a telescope with a 10 inch mirror, the scope tends to become quite large, and sometimes difficult to move out to the driveway, or drag out to the backyard. It may not even fit inside your car to take to a dark site or star party and when the scope is pointing straight up, you may need a ladder to look through the eyepiece. More Info You can also check out reviews of more telescopes by Sky and Telescope Magazine.