The Galaxy also comes stocked with slightly-wider tires, which will tend to require slightly less tire pressures and will offer a slightly more comfortable ride.

The components look pretty similar between the two. One difference is that the Galaxy has a Deore rear derailleur which is slightly more versatile than the Sora derailleur on the Mirage Sport, which is made exclusively for road use and is thus intended for lower gearing. From this is seems like the Mirage Sport is designed more as a road bicycle, whereas the Galaxy really is intended for commuting and city riding (more potholes, occasional rough terrain).

Being a commuter myself, I would probably elect for the Galaxy because I like the slight comfort advantage and robustness of the steel frame and wider tires and I don't mind a slightly heavier frame. They really are both very comparable, and swapping tires or entry-level derailleurs is fairly cheap anyway (and there probably will be no reason to do this in either case). The frame is the major difference. Take a look at this article if you're unsure which frame material you'd prefer:

http://www.sheldonbrown.com/frame-materials.html

I think you probably can't go wrong between the two. I think they're both good buys.