My friend, who is diabetic, tells me that the sweet potatoes with white flesh are better for BG but I haven't tried them yet. I don't like the ones with orange flesh much so I hope they also taste better.
To me, a sweet potato doesn't even taste like a potato so I always think what's the point? May as well have another (lower carb) vegetable instead. I find that if I am going to choose a substitute for something it had better taste (almost) the same, if not, forget it and try something else.