I have the 10 and 12mt. My weight is roughly 89kg and ride the Laluz 135.
The 12 is a great kite with good bottom and top end. I will get out in 14 knots anything less is just to hard. Personally I would not go bigger than the 12 as they become too heavy for lighter winds and very slow in turning with the type of construction compared to light wind kites.
If you consistently get 15-18 knots compared to 13-15 knots the 12 will work perfectly and once you are up in the top end range you will be able to handle it with no problems and boost very very big. It's true what they say "Plug it in and play". Very forgiving Freeride kite.
If you get more wind in the 13-15 range go a light wind big boy kite.
I did not even think about a 14 as the 12 will turn better, have just as good bottom end as the 14, as the 14 becomes heavy being bigger and have better top end.
I vote 12