For home use the 90 should be fine. Remember you are only making 1 -2 pies at a time at 90 seconds each! and can easily feed 30-50 people in an a few hours time once you get it mastered. The bigger you go = more $$,more wood, more heat up time ... If you are going commercial step it up to a 48 " !!
It seems to me you are a man of many means, and could save some$$ by building yourself. If money is no object just go for Tuscano100 If you are doing/building the stand the balance of the install is not that complicated? Forno gets a lot of $$ for a little stucco?
Look how great Flyboy4uall came out!! he did it all. very elaborate.