Their benefit is they can multi-class with the Cleric class. So they can be a: Fighter/Cleric (particularly good) Magic-User/Cleric (particularly good) Cleric/Thief Fighter/Magic-User/Cleric (good but extremely slow leveling) Fighter/Cleric/Thief Magic-User/Cleric/Thief So demi-humans all have the ability to multiclass well except the halfling. But in 2e you really see the evolution of this advantage where even halflings can become Fighter/Thieves.
Their benefit is they can multi-class with the Cleric class. So they can be a:
Fighter/Cleric (particularly good)
Magic-User/Cleric (particularly good)
Cleric/Thief
Fighter/Magic-User/Cleric (good but extremely slow leveling)
Fighter/Cleric/Thief
Magic-User/Cleric/Thief
So demi-humans all have the ability to multiclass well except the halfling. But in 2e you really see the evolution of this advantage where even halflings can become Fighter/Thieves.
Interesting, unless of course your DM doesn't allow multi classing