Rucker vs Hiking bag

I'm doing an overnight ruck event next month. We are told to expect 12-15 hrs and 15-20 miles. We are required to begin the ruck with a 30# weight and 6 liters of water. The water can be dumped, consumed, shared, etc. But the weight must remain for the duration of the ruck.

My question is this:
- Am I better off using my 55L hiking backpack or a borrowed GoRuck bag with hip belt, which is what everyone else will be using.

I've tried on the borrowed GoRuck, and the hip belt sits higher than is ideal, about 2 inches above my belly button (I'm 6'1"). That's the greatest reason I'm even considering my hiking pack > rucker.

• Thoughts?

• Are there any benefits to the GoRuck bag I may be overlooking?