What is the cons of using high temperature/low water to cook curry?
One con of cooking this way, high temp and less water, is that your curry is much more likely to burn.  Both lower temperatures and more water slow the cooking, making it easier to find the right spot where everything's cooked through and done, instead of overreaching the time or not stirring quite enough and finding the bottom burned.  It maybe can be done, if you're very attentive and keep stirring and measured everything just right - but it is riskier.

Another con is that longer cooking often affects dishes differently.  Cooking longer at lower temperatures gives flavors more time to meld, with ingredients reacting to each other or breaking down differently.  Depending on your ingredients or the dish's texture the spices may distribute unevenly if they don't have enough time to equalize (one reason stew, for example, does very well with longer cooking times).  Cooking at higher temperature for less time may also give you a very different effect - think garlic sauteed in oil versus garlic roasted with oil, very different flavors.  

Likewise, using less water may mean your ingredients cannot mix as freely, so they interact with each other less and it takes more time for the dish to reach the same melded flavor effect.  It is also a safer limiting factor - if the powder is cooked before enough water is evaporated to make it thick, the extra water can be simmered off.  If the water simmers down first, then the powder will not be finished cooking - which might be a bigger problem.  It will also be harder to correct, and will take more time since any water added at that point will have to heat before the powder can finish cooking.