Originally Posted by Ken
Just a guess from 26 years of windsurfing - .65 kg of weight difference between the WC and W boards will not make a noticeable difference in the planing threshold for the 144, especially for someone at your weight. I used the word "noticeable" since there probably is a very, very, very small difference, just not one that could be measured.
I still think the 150 is your best bet for your under 15 knots wind range. As for sail size, I can only speak to my experience with my largest sails - Maui Sails TR 9.2 and 11.0. There is a very noticeable difference in power and early planing between the two, especially between 8 -12 knots on my formula board. I weigh 78kg (170lbs).
Ken thanks for your recommendations on the iS150. About the sails, would you then recommend to go for a 11 m2 (e.g. Severne OverDrive) rather than a 10m2?