I haven't ridden the 9.6 quest ,only can go by people who told me its good ,did own a 9.5 mana for a while .
did move to the 8,10 then 8,5 .the mana shape full nose makes wave riding easy ,and gives the stability .
the no nose shape will be better for steeper waves ...I also had the 9,6 ,9.1 8,8 x32 hokua s ...lot s of rocker ..slower board but still rips.
the mana is easier to ride with nice speed.
if you have slower smaller waves ,the 9,5 mana ,
and as you said less volume ,