For side surfing the high brace is completely appropriate. A properly taught high brace should not be significantly higher than a low brace. The only difference between the two should be the orientation of the wrist: pointed up with the high brace so that the power face is against the water, and wrist slightly down for the low brace to use the back face of the paddle. With more lean the high brace will become higher, but a good lean is important in serious side surfing.
For straight ahead surfing, the low brace is probably more usefull. In the overall scheme of things, I think it would be hard to make a case for one being more important than the other. A skilled paddle should be able to use both.
>Hummmm, high brace vs low brace! From my perspective the low brace is grossly overlooked, but I feel in smaller waves is far more effective. With the high brace, the paddle will be approximately shoulder high and obviously has some distance to contact the water. To do so, the paddler must not only edge the kayak, but also lean the body yielding somewhat of a bell buoy effect. With the low brace, the backside of the paddle blade is very close to the water and only edging of the kayak is necessary. In my training progression, I always start students out with the low brace and emphasize the J-lean edging of the kayak. Having mastered that, they quickly move on to the High brace which in extreme situations is actually the last part of a traditional C to C roll. In white water, I use a low brace nearly 10 times more than a high brace.