The main advantage of predictive text is that it allows you to type a word with fewer taps of the keypad.
Also, this is helpful as it allows you to write the text faster – and it typically gives you the correct spelling of the word.
It is important to distinguish between predictive text and AutoCorrect, a popular feature on devices such as the iPhone. They use similar technology, but they are not the exact same. AutoCorrect analyzes keystrokes and corrects spelling and grammar mistakes, as opposed to predicting what the user types in based on the pressing of a few device keys.
Settings > General > Keyboard > Predictive