The MSI MEG X870E ACE MAX wins in 9 out of 13 comparable specs, with 2 ties. Its biggest advantage is LAN (300% better).
B660M DS3H DDR4 wins in 2 specs (PCIe x1 Slots: 100% better).
Recommendation
Choose MEG X870E ACE MAX if you want the best overall performance — especially lan.
Choose B660M DS3H DDR4 if pcie x1 slots matters more to you.
