To each, his own is the mantra here! Both bags are 100% waterproof, though the Frogman is built tougher and uses welded PVC fabric in the main waterproof compartment.
The Longranger Pro offers multiple layers of protection, with highly water-retardant and abrasion-proof outer fabrics, and then from an inner layer of waterproof, seam-sealed dry bag. Both are built like tanks and should see you through many memorable rides.