In addition to increased accuracy, Dragon Dictate has the ability to learn words you use often, and nearly always handles proper names better than the Mavericks Dictation tool. Dragon Dictate also has several additional features for controlling the user interface that are simply not available with the Dictation module in Mavericks.
In other words, Dragon Dictate is a fully developed, feature-rich product; Mavericks's Dictation, not so much. Then again, Dragon Dictate costs $200, while the Mavericks tool is free.
The way I see it, Mavericks's Dictation tool is like Dragon Dictate Lite. Nevertheless, I'm finding use for both of them. The Mavericks tool's best feature is the ability to activate it anywhere on my Mac and immediately start dictating; I'm using it in all sorts of unexpected places on my Mac. Dragon Dictate is not as easy to get working in any context, but when you need to dictate long passages of text, its increased accuracy makes it the clear choice.
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