Research depth
Discovery
How well the tool supports keyword, competitor, SERP, backlink, or market research before execution.
SEO.AI
Strong competitor/SERP-oriented research for content production, but not documented as broad market research.
The SEO writing page says competitor analysis and a score based on 5.7 million data points; the audit page says it analyzes top-ranking articles, NLP, missing keywords, titles, descriptions, and word count. https://seo.ai/features/seo-writing https://seo.ai/features/seo-audits
Surfer SEO
Good SERP and content research for page-level optimization.
Strong around term recommendations, outlines, and content briefs.