A battle between two searching heavyweights!
Conclusion
Its a knock-out!
For short, accurate searches, use MeSH
For extensive, exhaustive searches, use freetext WITH MeSH, to ensure the best result
In the blue Corner: Freetext!
Freetext searching means searching for key words and phrases in the title, abstract and some other fields of an article
This means that you may get many results which are not relevant, because they only make brief reference to your terms, and are not really focused on the subject you are searching for
In the red corner: MeSH!
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MeSH vs. Freetext
MeSH are medical subject headings
They describe what Medline articles are about
Searching with them ensures your results are more relevant, and you don't miss out on papers that use different terminology