Research depth
Discovery
How well the tool supports keyword, competitor, SERP, backlink, or market research before execution.
BuzzSumo
Exceptional breadth and historical depth for content/media research.
The Content Research page claims a 5-billion-article index, competitive benchmarking and five years of data (https://buzzsumo.com/content-research/).
SEOTesting
Broad first-party reporting and experiment research over Search Console data, including page/query, comparison, content decay, cannibalization and group analysis.
The product lists Search Console exports, page/query detail and comparison reports at https://seotesting.com/google-search-console-data/ and content groups at https://seotesting.com/features/.