The Seagate IronWolf 4TB wins in 3 out of 5 comparable specs, with 1 tie. Its biggest advantage is MSRP (23% better).
Barracuda 8TB wins in 1 spec (Capacity: 100% better).
Recommendation
Choose IronWolf 4TB if you want the best overall performance — especially msrp.
Choose Barracuda 8TB if capacity matters more to you.