They're pretty different tools. If anything, you would use Freshpaint to send data into PostHog.
PostHog is an analytics tool. Once you have data in PostHog, you can run queries against the data to produce various charts and graphs. Other analytics tool include Mixpanel, Amplitude, and Heap. The primary reason you would use an analytics tool is you want to ask questions about your users.
Freshpaint is a data collection tool. We automatically collect data from your site such as clicks, pageviews, etc. You can then use our UI to send that data to different tools. We integrate with the large analytics tools and also a ton of marketing tools like Intercom and HubSpot. There are two reasons you would want to use a tool like Freshpaint:
1) It's easy to collect data. Freshpaint instruments your entire site, so you don't have to.
2) It's easy to send the data to different tools. Once a piece of data is in Freshpaint, you can send it in one click to any of your analytics and marketing tools.
Does that make sense?