Wow, that's some pretty short runs (0.27 nautical mi. to 0.48 nautical mi.).
Yes, that would make for lots of gybes if the wind is 15 knots and you are sailing at 25 knots+ board speed.
The formula board will probably plane a little earlier, but it won't be quite so easy to gybe.
You can gybe a formula board, for sure, it's just going to take a little more learning/change from what you might be doing now in terms of gybing.
The Isonic has the potential for a bit more top speed and may be a little easier to gybe.
Since you are going for 9.0 and 11.5 m2 rigs I suspect that there's not much wind at your vactaion location... is this right?
The short distance will be "covered" pretty quickly on either board so I don't think there's a lot of difference there.
If you go with the Isonic 150 you may want to consider a slightly smaller rig as your largest.
I'm not sure you will gain alot with an 11.5 m2 over say a 10.5 m2 and if really early planing is your goal, you might be better with a more drafty free race sail.
Hope this helps,