Contact data is the least glamorous and most operationally decisive layer of a sourcing stack: the best search in the world produces nothing if outreach bounces. It's also the layer where vendor claims are least trustworthy, because accuracy varies enormously by geography, seniority, and industry — a vendor that's excellent on US mid-level engineers can be poor on European executives, and both experiences are 'true'.
The only evaluation that works is a head-to-head on your population: pull 100–200 real target profiles from live searches, run them through each candidate vendor (Lusha, ContactOut, RocketReach, SignalHire, Apollo all offer free tiers or trials sufficient for this), and measure find rate and bounce rate per vendor. The spread between best and worst on a specific population routinely exceeds 30 points.
Two structural notes from our testing. Personal emails outperform work emails for recruiting replies (candidates don't job-hunt in their work inbox) — which is why recruiting-first vendors like ContactOut emphasize them. And phone data is the widest quality gap between vendors: if your desks call, weight direct-dial accuracy heavily and test it explicitly.
Compliance is manageable but not optional. Under GDPR, sourcing EU candidates from public data generally proceeds under legitimate interest — but that carries duties: honor deletion requests promptly, keep data minimal and current, and be able to say where a record came from. US state laws (CCPA and successors) add disclosure duties. Practically: prefer vendors that document their compliance posture and deletion workflows, and route all outreach through systems that record consent and opt-outs.
Buying advice: credit-based standalone tools fit teams with an existing outreach layer; bundled data inside platforms (hireEZ, Apollo) is cheaper per contact but locks you to the platform's workflow; and agentic tools like Noon internalize the whole problem — contact finding and outreach happen inside the agent, so data quality shows up in its reply rates rather than as a line item you manage.