Given that they are both the same connector they are just different mechanism designs for the same function.
The bottom one is the most common connector that, once you've twisted the tapper in place, you pull the handle out and push it down till it locks to engage the CO2 and open the keg.
The top one dopes the same thing but, after you've twisted teh tapper in place, you turn the black handles till it locks in place, engaging the co2 and opening the keg.
The bottom one is, in my opinion, easier to operate correctly, even when in dark places, cramped quarters or when impaired (all of which were sometimes true at the bar I worked at years back).
Jason 'Kornkob' Robinson
I wanna move to Theory. Everything works in Theory.