AdGuard Home supports DNS over HTTPS and uses it by default (via Quad9). This encrypts your DNS requests and ensures your ISP can’t collect the queries or modify the responses. Some ISPs build an advertising profile for you based on the sites you visit, even if you use third-party DNS like Cloudflare’s 1.1.1.1 or Google’s 8.8.8.8. Using encrypted DNS prevents them from doing this.
You can use DNS over HTTPS with PiHole but it’s a lot of manual work to set it up. With AdGuard Home, you just enter the DNS server URL in the web UI, and that’s it.