I never quite got the whole "breathable hip boot" thing. Other than being able to wear your wading shoe, for perhaps better hikability in rough terrain, I don't know.
I use a pair of hogeman felt bottom boot foot with canvas upper for work around our trout nursery and they are a dream to wear. very comfortable.
From a small stream wading perspective, If you do a lot of climbing on rugger terrain and hiking, I be more concerned about the boot than the upper. Get a good pair of hiking shoes, (you are not in the water that much anyway) and something cheap that goes over the knee. Lets face it, how often are you in the water up to your thighs? Maybe like a neoprene knee high sock. Then you can wear loose knee length bermuda shorts and stay cool and dry on the foot.
I am strong believer with wearing waders ALL the time. Like wearing gloves or safety glasses when working with tools. THey are your only means of safety between you and the workplace. I broke that rule this summer on a canoe trip at the potomac. I wore sandals, it was comfortable and my feet got sunburnt, but I kinda liked it overall. Anyway, the next week I got overzealous and tried my new "wading sandal: on the susky. What a mistake, After slipping and sliding near the bank for ten minutes I finally kicked a rock and chipped a piece of my toenail off. That is painful in the following days. I'll NEVER not wear wading boots on the river again and always wear waders. It is creepy being waste deep in the water with those slurping catfish all around you.
Maurice