@anonymous_user_972c05d8
Glad to be of service!
To answer, it depends. It generates a relatively low-poly model of the landscape you’re selecting - but all of the buildings and landscape features, such as mountains and canyons, are still generated. In terms of the vegetation, and actual texturing of the model - the free version of the plugin leaves a lot to be desired. I usually add shaders and materials to it manually in Unreal after I’ve generated everything because you’re right, Quixel does this very well.
So maybe your best approach would be something of a cross between the options - using Unreal for the physical land features and vegetation while uploading models of the cities and roadways from the plugin, because the model of the cities, from what I’ve found, is very precise, even for low-poly. Just a thought, though!
I hope this can help some more! 
-Zen