I will go with rodprof on this one. The short length of mono gives just a little bit of stretch which may help keep a lightly hooked fish on, provides stealth and it much easier to cut, tie and untangle in the event of a tangle. Some may disagree with this, but in my case, I can toss the jig further with the mono top shot than I can tying the braid straight to my swivel. One other piece of advice, MAKE SURE that the boat you are going on permits braid. A few of the codfish boats now have an idiotic no braid policy.
Gamakatsu