To give you an analogy,
A birdeater is like a tall muscular man wearing a fur pelt over a hard leather armor armed with two large steel daggers.
An emp is like a stout muscular man wearing an iron plate mail with an iron shield and an iron flail.
The taller man is obviously quicker because he has less to carry around, but his defenses are rather lacking against the slower shorter man. Also, though the taller man can penetrate the shorter man's defenses, a direct hit is much more difficult for him and he can be kept at bay by the shorter man's shield while the shorter man retaliates by bashing the taller man with the flail. Additionally, the shorter man's shield may also be used to bash against the taller man as an additional weapon.
Now, for scorpions like the deathstalker, imagine the same stout muscular man wearing a chain-link mail instead with a smaller shield, but a deadlier flail with long pointed protrusions.
A birdeater is like a tall muscular man wearing a fur pelt over a hard leather armor armed with two large steel daggers.
An emp is like a stout muscular man wearing an iron plate mail with an iron shield and an iron flail.
The taller man is obviously quicker because he has less to carry around, but his defenses are rather lacking against the slower shorter man. Also, though the taller man can penetrate the shorter man's defenses, a direct hit is much more difficult for him and he can be kept at bay by the shorter man's shield while the shorter man retaliates by bashing the taller man with the flail. Additionally, the shorter man's shield may also be used to bash against the taller man as an additional weapon.
Now, for scorpions like the deathstalker, imagine the same stout muscular man wearing a chain-link mail instead with a smaller shield, but a deadlier flail with long pointed protrusions.