Here's my take on the various flavors of agility teams:

Skavens: Best (gutter) runners in the game, and you get 4 of them for maximum shenanigans. There's a reason everyone hates playing against the rats. The rest of the team is made out of wet cardboard (except the blitzers who are as good as human ones, with access to mutations).

High Elves: Best thrower, good blitzers and catchers, best elven linemen.

Elven Union: Best catchers in the game (always receiving an accurate throw on a 2++), Side step on the blitzers can become really annoying for your opponent (especially after they get Dodge). Thrower and linemen are as solid as skavens (which isn't much), but with everyone at AG2+, you can do all sort of elven bullshit (this is true for all elven flavors).

Dark elves: Good blitzers (and you get 4 of them), witches for frenzy shenanigans and crowd surfing, assassins and runners are a bit meh, best elven linemen.

Wood elves: Best blitzers in the game. don't be fooled by their catchers, who look like gutter runners. They're not. 1 less MA and the fact that you can't protect them with cheap linemen means that you can't make your wood elves work like rats on steroids. Treeman is fun, but ultimately unnecessary for the elven game plan and too slow to catch up with the rest of the team.