RE: iSonic 105 or 101 ???
With the 2007 101 you will get a mild advantage in speed mainly due to refinements in trim/control (allowing for hard/er riding at top speed) ... it's not huge c/w 2006 105, which is still a fast ride, especially in open water fully powered slalom blasting.
Jibe/control on the new board is definitely improved in 2007, it's a standout in the new iS line.
Please let us know if you need more info etc.
Cheers ~ Ian