There is not much of a difference the way I fly. Let me explain.
First, one should use flaps up stall speed. I think the speeds noted above are for flaps down. Then, take flaps up stall speed times the square root of the design G. That should be close to maneuver speed.
The 6 G factor is at a reduced weight of 1550. That would be about 5 G at 1800.
I think we are talking about a design differenct (at gross weight) of about 4 for the 9 (probably 3.8) and 5 for the 7 and 8. Anybody have the real design numbers? CAST says 3.8 for the -8 but that is not correct for setting Va, I suspect.
The 9 has a lower Va or maneuver speed because of the 4 G design and lower stall speed. If Vs is 59, then square root of 4 x Vs is 118. For the 8, if the stall speed is 64, then square root of 5 x Vs is 142 (just an example until we get the real numbers).
I suspect Pierre pulls Gs all day long, perhaps there is a distinct difference between 4 and 5 Gs for him. For me, there is not much difference between 4 and 5 Gs. I never get close. Either one is too much for me.
From a practical standpoint either airplane is ok with me.
Aerobatics are another matter. With the low Va for the 9, you can pull a lot more Gs with less speed which makes it more difficult to get in and out of aerobatic maneuvers.
I would suggest that you not steer away from the 9 because of the maneuver speed unless you want to maneuver (as in aerobatics).