Well, if you want a lazy, but serious answer:
"[Eldar] are long-lived by human standards, and most will live more than a thousand years unless they die from accident or disease (However, Humans can still live for hundreds of years via rejuvenat treatments, and Space Marines are effectively immortal). Eldar also have much faster metabolic rates than humans, and their cardiac and neurological systems are more advanced. These traits manifest in their vastly heightened reactions and agility compared to humans. To them humans seem to move in slow motion with a certain degree of awkwardness, while to humans the Eldar can move with distracting grace and can be blindingly fast in combat (Basically, if you saw a Human and Eldar in motion together, the Human would like like they were moving at 30 FPS, whereas the Eldar would be like 60+ FPS. They're just smoother and more graceful in everything they do). As a race they have a high level of psychic ability, which serves as the foundation of their technology. The Eldar that actively cultivate their psyker potential seem to exhibit a much-extended lifespan as well, one proportional to their prowess. The Farseers of the Eldar can live for several thousand years. Eldar are mentally far superior to humans, and feel all emotions much more strongly, requiring the Eldar to exercise constant restraint to avoid mental breakdown (aka Dark Eldar)."
As far as I'm aware, there's pretty much nothing that Eldar aren't better at than regular, unaugmented humans. At a glance, one might be tempted to say that they're more fragile, but that has more to do with their military doctrine and cultural fighting styles rather than how they are biologically. That being said, Humans aren't at constant risk of losing their souls to Slaanesh, and they're also not in danger of going extinct, so there's that.