The Orca bags use heavier more durable material than the Dolphin panniers and the type of construction differs significantly. The Orca’s use welded construction and the Dolphin panniers are sewn and taped to seal the seams. Both are waterproof and are equipped with the Cam-Lock mounting system. The advantage of the sewn & taped Dolphin panniers is that we can sew pockets to the outside and seal the seams once the sewing steps are completed. In the Orca construction, the welding process uses moulds that make outside pockets with any volume (3D) difficult but flat 2D pockets possible. Dolphin panniers are lighter than the Orca panniers so ultimately it comes down to what features and look you prefer.