Upvote:6
You won't have a choice: you'll go through US preclearance in Dublin. When you arrive in Dublin, you'll follow the signs to your gate, which will take you through security screening and preclearance.
Your flight from AUH to DUB is shared by many passengers not traveling to the US, so preclearance in AUH is not possible. Everyone on the plane must go through preclearance, and the flight must proceed directly to the US. So preclearance can only be done at the last airport you touch before flying to the US, if it's available there.