Here is a table describing the pros and cons and appropriate uses for search engines and subject directories on the Internet.
| Search Engines | Subject Directories | |
| Pros | – fast – usually more up-to-date than directories due to crawling and automated indexing algorithms – millions of hits, so the chance of finding something relevant and up-to-date is high (as long as you have the patience to slog through all the results when you are looking for something a bit obscure) – can handle complex queries involving more than one subject at a time |
– selected and vetted by humans (usually), so quality of results is sometimes higher than with search engines – good when you are looking for a broad range of information on a particular (single-issue) topic – the ones that are done by volunteers often don’t include advertising – usually don’t attempt to rank sites, so a minor site with good information can be found in the same place as a major site with good information – results tend to be limited to a few pages rather than millions of hits so it is possible for the user to check each link if necessary – can sometimes include sites that search engines miss or don’t rank highly |
| Cons | – not all search engines are unbiased — some may give preference to sites that pay to be placed at the top of search results or pay for advertising in general – usually include advertising – ranking is based on algorithms, but algorithms sometimes miss out on sites with good content |
– hard to maintain, so they get out of date quickly – not as useful for finding information involving several topics/issues at once (e.g. thyroid disease AND diabetes in Asian women over 60) – sometimes you have to go down through several directory trees to get to the subject you are looking for (slow) |
| Appropriate Uses | – good place to start a search – definitely the best choice when you need a quick answer to a question and the authority of the site or reliability of the data is not your primary concern – better for cases where the most recent information is necessary |
– good place to start a search – good way to get a broad overview of a subject – probably better than search engines for certain subjects, or information on particular geographical areas |
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