If I had to choose one method for competition then I would choose quotes over non-quotes. This is because Google and other search engines give nice relevancy points to pages that have exact matches of the word on them (this is true even on searches conducted without quotes). Exact matches get enough of a relevancy bonus that one could argue that someone without an exact match of your keyword is not really competition (unless of course they can trump you by having massively more back link anchor text and/or PageRank than you do). I remember joining in a related discussion about this a while back. The title of the thread was: Is WordTracker's exact match reasoning flawed? [webmasterworld.com].