I have both a Reload backpack (the fullsize one) and an Ortlieb. The Reload is badass, but SO SO SO big. Almost too big. I started using the Ortlieb when I didn't have as much to carry because the Reload was so big. It can definitely come in handy, but when you don't have alot to carry it may be too much.
The Ortlieb is nice, but the lack of subdivided compartments is a little frustrating. Can't beat the price though!