Asphalt 5 is Gameloft's fifth Asphalt title, but only the second in the series that can be found on the iPod and iPhone. Besides running a bit smoother on newer hardware, one of the most noticeable differences is the "bloom" effect. This creates highlights over every object in the game, and can sometimes mask jagged textures or polygons.
There is no option to turn this effect off, but it shouldn't bother players too much. They'll probably be too busy focusing on what's around the next curve.