I never lived on a 15 but I have lived on a 22 and for many years lived on a 26. I now live on a 34 (largest boat I ever had was 42 but I lived on my 26 at the time and raced the 42) and don’t think I will get much larger then that. When you think about the 3 foot reach it’s not just that the boat is 3 feet shorter but instead the boat is shorter, narrower and much lighter. When you change the length of a boat you are changing something in three dimensions and the effect is much greater the just the change in length. Add 3 feet and add sail area, docking expense, strain on sheets and other rigging, larger anchor etc. Three feet is a large change when you are talking about 30 to 40 foot boats.
All the best,