I would say Transmission has simpler UI. Outside of UI, it's also packaged differently, compared to Qbittorrent, Transmission can be installed completely headlessly without dependencies to QT/GTK+X.
In terms of actual features, Transmission is more lightweight. It doesn't support super-seeding, broadcatching, native SOCKS support and doesn't have built-in search engine integration.
It only provides a web ui which is inferior to the standalone ui version.
If you want to go that route you might as well use Deluge, which is built on the same libtorrent library, has a proper daemon-client architecture with fully featured native clients for all major platforms.
What settings would the average user find useful beyond adding a blocklist (which Transmission supports)? Genuinely curious as someone who used Transmission back in the day and appreciated the simplicity.