There are way more effective ways to describe facial expressions in prose. Personally when I want to force the reader to think about and picture an expression I like to use a weirdly specific example of it. So instead of 'Billy looked disgusted' I'll say something like 'Billy made a face like he was trying to hide bad oysters under his tongue'.
The only time I would bother with emojis in comics is when you can't see the speaker in the panel, and their emotional state while speaking is important and not conveyed by the content of their dialogue.
So like if they're saying 'I'm happy' it's not necessary. If they're saying 'I hate you' but with a smile on their face, 'I hate you :)' conveys an entirely different message.
Just personal preference and opinion, though.