I guess the main advantage of feature branches is that you can easily drop them if it turns out the feature was a bad idea or too hard to implement.
The advantage of trunk based development would be that the feature gets potentially more testing. Same goes for interactions with the main line code - if feature development breaks the core in subtle ways, it will be noticed earlier using trunk based development.
It will be noticed - by angry users. Which is why untested continuous deployment is madness.
When you do checkpoint regular releases done often, you get a chance to smoketest and block a release. Automated smoke tests only go so far in fixing this - if you could cheaply, reliably and completely fully automate testing, everyone would already do that.
About the only way to do continuous deployment is to not deploy into production but use lagged deployment practice...
Yes - in my case the "users" are just my colleagues (and yes, they could get angry, but the feedback can be worth it).
I believe that "trunk" is not commonly meant to be immediately deployed to users. But, maybe things are different in the web world, where "deploy" is as easy as "upload to server"?
The advantage of trunk based development would be that the feature gets potentially more testing. Same goes for interactions with the main line code - if feature development breaks the core in subtle ways, it will be noticed earlier using trunk based development.