Depends on who you ask.
Thyroid doc that is controled by the drug companies, $yncrap is best.
A thyroid patient the has tried both, in both case had the "proper" dosage, 99.9% will say Armour or other desiccated thyroid medication.
Like the tag line on STTM says, did not work, does not work, never will work. This is about $yncrap.
My wife started on synthetic, changed to Armour, will never go back. The change was in less than 2 weeks, and it was dramatic.