This is a difficult question to answer because the viewpoint changes for each person (i.e. a librarian and a student, for example, will look at information in a different light even though they use both subscription services and free access search engines). This post attempts to answer this question by breaking the question down.
Why are paid searches better than free access searches?
Paid search offer a better interface. Subscription services are less likely to change their interface as regular as free access search engines. This allows a user to get used to a specific interface, which, inturn, is better. From an interface perspective, subscription services are more involved and in-depth.
As part of an interview a librarian stated that people are more likely to look at the first (or second) page of free access search engine, such as, Google. This is not the case with subscription services.
What is the added value of subscription services?
The short answer is ‘quality material’ can be access via subscription services. The longer answer, albeit slight, suggests that subscription services are extensively connected. For example, academic journals are linked to other journals which can be easily found by the searcher, such as the ‘cited by’ feature. In other words, subscription services know what an article is, how/why it is connected to another article. Free access search engines (i.e. Google Knowledge Graph) are starting to build up these connections, but they have a long way to go.
What is the added value to subscription services?
Quality of material. Instant access you might not get to go beyond. Academic databases are starting to get indexed by Google crawlers. BBC and Wikipedia get precedence. Better interface, post search tagging options (even if not thought of search terms), usability is a lot better. Instant access. Can’t beat library catalogue from each institution. If you’re paying for subscription services, you’re crazy not to use them. Could get lucky with free access search engines, sub subscription you get.