I would say they are about the same. The Sylvania Xtravision is one of those high-output street legal bulbs...sometimes referred to as "30%" bulbs because they typically (according to the manufacturer) are "30%" brighter, as well as being a tad whiter (say 50-100K). GE also has a version of a high output, called HiOutput, with bulbs sizes ending in "HO" ie. 9003HO.

Basically, they have different mixtures and tighter filament winding. Of course, you don't get something for nothing...bulb life is less than a normal or long-life bulb. These high output bulbs (depending on the company) are the basis of FMVSS108-compliant "blue" bulbs.