The differences of each race in Aion
In a word, the differences in each race of Aion are only appearance, location-based, and skill-based. According to which race you choose, you will begin from a different area. Neither has better stats, but some of the skills for certain classes differ depending on the race you selected. For instance, a specially stat-boosting skill for the Elyos may raise one stat, while the Asmodian version of that skill will raise a different stat.
Another difference is color of race in game (aion gold). The color palette for Asmodian skin tones has a selection of cold hues, ranging from ghostly white to purple, green, blue, etc. The Elyos skin tones are a much warmer variety and are more or less normal human complexion colors including ivory, peach, russet brown, tan, yellow, etc. Next would be the ornament on the back of each race. The Elyos have a yellow scarf, while the Asmodians bear a spiky, gray-haired mane, supposedly developed to help insulate against the cold, harsh climate of their world. One of the biggest differences can only be seen when each race draws its weapons with different level (aion kinah). While an Elyos more or less remains the same physically, an Asmodian's eyes begin to glow red.