Use all three, for different jobs, rather than choosing one. Broad match casts wide and belongs on a capped discovery budget; phrase match narrows to searches containing your keyword in order; exact match targets that search intent alone and is where proven converters and the bulk of your spend belong. The standard flow is broad and automatic campaigns to discover terms, exact to scale them, with negatives stopping the layers bidding against each other.
What each match type actually does
Broad matches searches related to your keyword, including terms with additional or reordered words and related concepts. It is the loosest, and produces useful and wasteful terms in roughly equal measure.
Phrase matches searches containing your keyword as a sequence, with words allowed before and after. It is the middle ground and often the most neglected of the three.
Exact matches that search and its close variants only, giving you direct control of the bid on one intent.
The mistake that costs the most
Running the same keyword in broad, phrase and exact without negating it downwards means your own campaigns compete in the same auction. You pay more for a click you were going to win anyway. Once a term is in exact, negate it in the looser layers.
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