Dubs can be good in shows where there's a lot of fast dialog; it's hard for subtitles to keep up. The loquacious protagonist of Steins;Gate benefits _significantly_ from a dub, for example. I watched the show twice when I realized the subs had skipped half his dialog.

Period accents are another place dubs can have an advantage, particularly in shows like Baccano! where the characters are ostensibly speaking English to start with.

It can also vary by localization studio. I didn't care for the English Spy x Family dub, but to my ear the Chinese dub is just as good as the original Japanese. For some reason the actors in many English dubs seem to have a hard time "really going for it" when a scene requires an over-the-top outburst of emotions.