I buy discounted "water" shoes from someplace like Sierra Trading Post. Remember to buy a shoe at LEAST a 1 size bigger or more than your street shoes to accommodate heavy socks/ neoprene gators.
   
I think a sticky traction sole for wet rock is key as well as light and comfortable, TOE bumper too.

I also like CORD LOCK's on shoelaces so you don't have loops to catch on roots.

I think ankle support is over-rated in that it's your muscle/tendon strength that supports your foot/ankle action.

Now ankle IMPACT protection is another thing. You see plenty of NBA players wearing low-cut shoes now and they twist and turn their ankles with more sheer force than we will on a portage.

Now IF you have a previous ankle injury from sports/accident and have actual physical damage then a higher boot laced tight or one of those slip on ankle/foot braces might be needed.

  I don't think there IS one perfect boot because everyone is a different size, the  load they carry, body weight, the way the walk, all play a part.

Traction on the other hand, is pretty well a constant.

IF you have "weak" ankles that are NOT orthopedic injury related ( like pins in ankle), get yourself a cheap WOBBLE balance board. You can find buying/info exercises on-line.

Remember indigenous people around the world carry loads like the old time Voyager's on mountain goat terrain for hours wearing little tire tread sandals or barefoot.

I'm NOT saying a higher/stiffer boot is bad, but there is a tradeoff in weight/comfort/drying and you might be better served with a good sole and a little "work-out" routine for you ankles/lower extremities.

  There are also numerous ways to lace a shoe or boot to keep it on your foot in muddy conditions and give more lateral support too. All can be found on-line with a Google search.