The ">>>>" was an exaggeration, don't mind it. It was just to say that WB pirates were portrayed to be superior to regular yonko pirates in the manga, but of course the gap isn't big. Just that i'd take WB's firstmate over any other yonko firstmate, i'd take his secondmate over any other yonko secondmate to the point that i think WB's secondmate may compare to a regular yonko firstmate.
WB was never interested in becoming pirate king, but it's been mentioned by multiple characters(Garp, Doflamingo and so on) that he could have been pirate king anytime he wanted to and was ruling the seas while sitting on top of the throne. Of course without their captain(as powerful as a pirate king) they will be weaker than a yonko crew but that's not the point.
The point was to show how even without their captain, without Ace, without Thatch, without Teach(who later became yonko himself), with Jozu crippled, they were still considered as contenders for the yonko title before getting overwhelmed by Teach's group(who became the yonkos in their stead). The fact that it's by defeating that crew that Teach became a yonko to the world's view is proof enough how that crew was portrayed to be of a higher caliber than normal yonko crews