What is the relative effectiveness of Internet search engines versus searching for information in a library or searching for a product in a grocery store?
IT depends on what you are looking for.
I can hardly find anything except milk in a grocery store. My nearest library is eight miles away, and they can only search the internet and the county library system. The next nearest real library is 35 miles away, and parking is hard to find.
So does effectiveness include my time? If the information is recent, or current events, the Internet is great. However, if I am looking for original material and it is before 1970, the Internet is awkward and lacking.
You have to define the measure of effectiveness to answer the question, as well as what you are looking for.