as a snowkiter i d prefer the 12 than my 15 dlx, i can edge easely on snow, thx to the snowboard and going upwind easely while working a kite ( used PL kites a bunch of time and those kites are sinned all the time....my shoulders can't hold working kites anymore), i don t have flat areas, all slopes and the 12 would be more nimble for looping up the hills....
on water, i prefer a parked kite, but past 12 knots, i guess i d use a 12 instead of my 15, more nimble if i want to go straight downwind.
the 15 saved me many days where i d have stayed on the beach if i had the 12.....
otherwise, my 15 is parked fast and still have a good high range and it is still my usual kite for 80% of my rides, snow or water.....i d be slightly/huge underpowered with a 12 or i should call God for a higher wind speed.....