Both systems contain cases, statutes, regulations, law review articles, legal books and practice materials, and news.
All of them have a means to check if a case is still good law: Shepard's in Lexis, Keycite in Westlaw.
All three systems contain 50 state charts, comparing statutes or the law between states.
Books and practice materials: Each system contains different publications by different authors. LexisNexis and Westlaw publish certain treatises, formbooks and other materials, so, obviously, the tendency is for LexisNexis publications to appear on LexisNexis, and Westlaw publications to appear on Westlaw.
Lexis databases include some important content published by Westlaw, namely:
Lexis DOES NOT include American Jurisprudence Legal Forms 2d, American Jurisprudence Proof of Facts (AMJUR-POF) or American Jurisprudence Trials (AMJUR-TRIALS ) .
Statutes and Regulations: All three databases contain statutes, codes and regulations for the federal government and each of the fifty states. Codified statutes in Lexis and Westlaw are Annotated, meaning they contain case summaries pertinent to the code section and other research references. Federal regulations also contain annotations in Lexis and Westlaw.
Cases: The systems mostly contain the same cases, but there may be a case that is on one system and not the others. Most cases in Lexis and Westlaw have Headnotes summarizing the points of law in the case, and can lead to other cases dealing with the same issue.
Headnotes are assigned a number. In Westlaw, it is called a Key Number. Westlaw has the Key Number Outline and ability to search by key number. Lexis Advance ties case headnotes into a new Topic Index. One can get topic documents, create an alert or view topics in an index.