The Thing is the far stronger of the two, has the superior durability and endurance.
Both are exceptional hand to hand fighters.
Savage Dragon has the better reflexes abnd agility and is blessed with a healing factor.
However, SD's healing factor does not prevent him from being KO'ed or from getting broken bones in the past.
SD has had his bones broken and then they healed at weird angles. He had to get Mighty Man to rebreak and reset them.
The Thing's strength would be also sufficient to break SD's bones.
The Thing for the win.