I tried DietPi on a new card, and it have more memory consumption (a little) and is + 2 °C hotter then the same installation with Raspberry OS. I use it for Pi-Hole, Unifi Controller and NAS.
The only difference i used ProFTPD instead Samba. Disabled the serial console and video output. Don’t know why it get hotter… any hint?
well, DietPi is not an own OS. It’s a set of bash scripts on to of a Debian based image. If you are running a Raspberry Pi SBC, we use Raspberry OS as base image. But it’s an extreme slim/diet version of Raspberry OS. We did a comparison between plain Raspberry OS and DietPi https://dietpi.com/stats.html
On a default installation, DietPi will have half of packages installed compare to a normal Raspberry OS, resulting in a lower memory footprint.
What Raspberry OS image did you compare with DietPi? Did you used same architecture? Did you updated Raspberry OS to latest available package version as DietPi is doing during installation?