The older one (X470) uses like 10W less on idle.
For me, that's important.
I believe the B550 also uses less, but I never used it.
Both are rock solid (pun intended).
Note, I only used them in a Asrock 1U enclosure combined with memory (ECC) from the Qualified Vendor List.
I used to use Xeon E3 processors icm with Supermicro servers for the low power systems.
But was fed up with the java IPMI implementation. Although, I must say, the asrock solution is not perfect either. Pretty finicky I must say.