The Corsair HX1500i wins in 3 out of 9 comparable specs, with 5 ties. Its biggest advantage is Wattage (76% better).
MPG A850G PCIE5 wins in 1 spec (MSRP: 63% better).
Recommendation
Choose HX1500i if you want the best overall performance — especially wattage.
Choose MPG A850G PCIE5 if msrp matters more to you.