SWT#3 seems to lean more to the Blueberry side and has a deeper,fruity flavor.SWT#3 also produces rock hard nugs.
SWT#4 seems to lean more to the Sweet Pink Grapefruit side and has a sweeter grapefruit flavor,the buds aren't as tight but I managed to get both #3 and #4 to mold.
#3 looked more stable and had better yeild, resin, and flower/leaf ratio. I also found it leaned more to the grapefruit as it is a backcross to it. I did get one bb pheno that was delishious. They will both mold on you. IMHO #3 is far better than #4.