Yes please consider the software, not just the form factor. Because SteamOS is Linux there is no Photoshop and Lightroom. There is however Gimp and Darktable (and Krita) which may or may not fit your needs.

Also you want to make sure you install desktop software as Flatpaks. Lke others have said, the root filesystem is read-only, and pacman repositories are old. The root filesystem gets reset on SteamOS updates, but flatpaks are installed in your home directory which persists across updates.