Is it beneficial to prefer keywords complementary to words in the title?
Key-words are crucial for indexing, whereas the words chosen for the title and the abstract are impactful for free text searches.

For instance, you may search PubMed with key-words (using the [mh] tag), with title words (using the [ti] tag), with title or abstract words (using the [tiab] tag), and so forth.

In case you use in the title and abstract words which correspond to indexing terms, then you may find reasonable to use alternative words as key-words. However, the most important thing is to use, in at least one of the venues (key-words, title, or abstract), the accepted indexing terms.