My verdict: the massive database for hard-to-find contacts.
RocketReach is useful when classic tools aren't enough, but expensive for what it is. The database is large (700M+ profiles), but quality is variable. Pricing is high: starting at $53/month for 170 lookups. If you're looking for hard-to-find contacts or outside LinkedIn, RocketReach can help. But for classic B2B, Apollo or Dropcontact are better.
What I like less: the high price for few lookups, the uneven data quality, and the fact that for standard B2B, other tools do better for less.
My advice: use RocketReach only for specific searches where Apollo and Dropcontact fail. For classic B2B, start with Apollo (free) or Dropcontact (GDPR-compliant data). RocketReach is a complementary tool, not a primary tool.