Both men are traditionally wrestlers, but at this point, they are mixed martial artists that have developed their all-around games.
Demetrious Johnson typically uses his striking to set up takedowns. He only holds three career knockouts, all of which came before the UFC. He has decent leg kicks and hands, but his speed is his biggest asset.
Joseph Benavidez has some of the most underrated striking in MMA. He does use it to grab takedowns, but he also uses it to end fights. Though he only has four career knockouts, two of them have come recently, putting away Rani Yahya and Yasuhiro Urushitani with his hands.
Benavidez definitely gets the advantage here.