United Airlines: Often offers daily nonstop services DUB–EWR with multiple cabin options, good network connections at Newark Liberty International Airport (EWR), and strong loyalty benefits for United flyers. Aer Lingus: Historically operated competitive transatlantic routes and can offer good value on nonstop flights with friendly fares and complimentary meals on long-haul, but seat pitch and extras vary by fare. Delta / American: More commonly present on one-stop itineraries via their U.S. hubs; good for frequent flyers with elite status or when nonstop fares are high. 
For December travel, prioritize nonstop carriers to reduce connection risk from winter storms. Compare included baggage, seat comfort, and change/cancellation policies — especially important during the holiday season. CTA: Compare nonstop and one-stop fares for your December dates now and book the option that balances price, schedule and reliability.