The verdict
If you can only do one, ask who has spare time. For a B2B team with a salesperson ready to follow up within hours, I'd pick Leadinfo. It pays back when someone acts on the alerts. For a team with a weak landing page and no budget, I'd pick Clarity. It is free, and a few real sessions often show the cause within minutes.
No cost stops you from running Clarity first, because it is free. Add Leadinfo later if your buyers are businesses and the traffic is steady. Skip Leadinfo for consumer sites and low traffic. Skip Clarity as your only tool if you need on-page surveys or deep funnel work.