Ei Compendex is an engineering bibliographic database published by Elsevier. It indexes scientific literature pertaining to engineering materials. Beginning in 1884, it was compiled by hand under the original title of Engineering Index. The name "Compendex" stands for COMPuterized ENgineering inDEX.

SCOPUS calculates the h-index of an author or a group of authors using journal publications from 1996-current, i.e. papers published before 1996 are not included in the calculation.

The h-index “gives an estimate of the importance, significance, and broad impact of a scientist’s cumulative research contributions”.    

please see the link

http://mggu-sh.ru/sites/default/files/h-index_and_impact_factors.pdf

both are indexed by Elsevier

This is hardcore business oriented differentiation of popular publications

Ei Compendex and Scopus are both large, multi-disciplinary databases of scientific literature that are used to index abstract articles, conference proceedings, and other types of scholarly works. They are both used as a tool to search for, discover, and assess research in a wide range of fields, including engineering, technology, and natural sciences.

Ei Compendex is maintained by Elsevier and focuses on the engineering field. It covers articles from conference proceedings, as well as journals, covering various engineering disciplines such as electrical engineering, mechanical engineering, and computer science. It is considered one of the most comprehensive engineering databases and is widely used by researchers and engineers in the field.

Scopus, also maintained by Elsevier, is a broader database that covers scientific literature in all fields of research, including science, technology, medicine, and social sciences. It provides a more comprehensive coverage of the scientific literature compared to Ei Compendex but has a smaller focus on the engineering field.

Both Ei Compendex and Scopus are well-respected databases in the scientific community and are widely used by researchers, librarians, and others in academia to locate and evaluate research in their respective fields.