I Know 2
First is Alter/Ego
Which really has no Pros other than it's free
OR
You could buy a Vocaloid 3 / 4 Produced By Crypton Future Media ( Price Range $169,95 to $199,95 )
Which includes more than one japanese VB, an english VB and a vocaloid editor called piapro studio which can be used as a VSTi Plugin, it also includes the DAW Studio one 3 ARTIST