Typically, my brush has the flow and opacity turned down anywhere between 50% - 75%, maybe lower depending on the situation. Its also set to adjust size and opacity based on pen pressure. To smooth out the colours I'd just continuously just go over the sharp areas a few times, depending on how smooth I want the transition to be.
I can't really say for sure which method is faster, but considering that you'd probably have more control and would only have to stick to one tool to get the painting done then its probably safe to say that this one is more efficient. Don't be afraid to just try out other different methods and see what result you like best.