I can't answer for OP but I think Tridactyl's callback hint mode is more powerful than Qutebrowsers' spawn, as we provide the hinted element to the callback. That means you can do stuff like remove it from the page or make the font comic sans etc. Qutebrowsers' spawn hint mode seems to only let you use the URL of the hint.

In general we seem to have more hint modes - copy paragraph to clipboard, select text, etc. See https://github.com/tridactyl/tridactyl/blob/5e8f94ff06bd5f14... (and forgive the code ... we really need an argument parser).