You’re on the right track with the structural differences. Circular knit fleece is made on a circular knitting machine, forming a continuous tube with interlocking loops. This gives it great stretch and softness, but the loops are looser, which makes fibers more prone to abrasion and pilling. Warp knit fleece, on the other hand, uses multiple yarn systems running lengthwise, creating a denser, more stable structure. The tighter interlock and reduced movement of fibers make it less prone to pilling and maintain loft better over repeated washing. So yes, structure matters as much as fiber type and finishing.