OK, here is my thoughts on the subject. If you are going during a time of high temperatures (would depend on how much you sweat) I would not suggest carrying a big backpack. I had a mini backpack for my recent trip and it held everything I wanted, but I could not carry my video camera.
I would not attempt, myself, to carry my video camera with a camera bag that is shoulder strapped. It just gets too heavy for me.
I personally like to carry a bigger backpack with me, but I would not do it if the temperature is over 78. The larger backpack will hold both the video camera, the digital camera (or SLR or point & shoot, whatever you have), plus drinks, maps, and extra clothes.