Fire: A hell of a lot of fire damage, from dragons, RORs, mages and mages who RIDE DRAGONS, you will laugh at anything weak to fire.
Even Silver Helms aren't bad for the price, and Ellyrian Reavers are some of the best light cav in the game. They won't beat Grail Knights, Blood Knights or Demigryphs, but damn they are sturdy (due to their physical resist and fire resist) and having high charge bonus.
Cavalry: Dragon Princes are some of the most cost effective heavy cav in the game.
Magic: You currently have access to the most lores of magic in the game, having all the generic ones and a unique one for your own.
Either way, this ability could use some rework. To some people, this ability was poorly adapted from the tabletop rule, for the tabletop stated the ability allow the HE to strike first no matter how injured they are, making it more of an offensive ability than a defensive one. This make you by far the most durable of the Elven factions, unlike your edgy or hippy cousins, most of your units can actually take a hit or two.
Martial Prowess: Their passive ability, Martial Prowess, gives you 12 melee defense and 2 melee attack as long as you are above 50% HP.
It also means that they can land the first blows of battles. Their cheapest archers can out range and kill a lot of elite skirmishers in a shootout.
Range: Their range units can dish out a hell lot of damage.
If the Empire is a Jack of all Trades, you are a Queen of all Trades.
Versatility: An all around very well balanced roster.
You have a high tolerance for silly headgear.
Because you probably played them on the tabletop and this is the closest thing to 9th edition we will have til Warhammer: The Old World comes out.
You like armies that don't really have a field where they are particularly weak in, and are just solid all around.
Because you want an excuse to act like a snobby prick.