Both are great. Unraid makes things really easy with their Community Apps feature. On the technical side, I prefer TrueNAS Scale because it’s based on Debian, whereas Unraid is based on Slackware Linux. TrueNAS Scale is fully FOSS, whereas big parts of Unraid are proprietary. But there are more guides and tutorials for Unraid, as it seems to be the more popular option. If you’re going to install Unraid, definitely check out Spaceinvader One on YouTube, he’s got some awesome videos on the topic.