The verdict
If you can only run one, run Google Analytics. It is free, it covers the quantitative ground (acquisition, conversions, channel attribution) that every business needs, and it is already wired into the Google tools you are likely paying for. Nothing else clears the value-for-money bar at zero cost.
Reach for Contentsquare the moment quantitative numbers stop being enough , when GA4 says a checkout or signup flow is bleeding users and you need to see why. Its session replay and heatmaps are exactly the qualitative layer GA4 deliberately does not have. The Growth plan from 40 USD/mo and a free tier make it accessible to a small team, which was not true of the old enterprise-only Contentsquare.
The trap to avoid is buying Contentsquare instead of GA4 expecting it to replace channel and conversion reporting. It is a behaviour-analytics platform, not a free replacement for Google's measurement stack.