Better than the Smartphone

Fits in my pocket better: it's thicker, but smaller in the other two dimensions
Battery lasts for days, not hours
Speakerphone is somehow better
Voice calls have lower latency: I don't feel like I'm interrupting people
FM Radio
Almost no compulsion to "check my phone": I know there's nothing going on there
Conversation starter: nearly everyone who sees it wants to tell me about a fond memory of a featurephone they once used

Same as the Smartphone

Camera is just okay
Group SMS displays a blank subject before every message
Google Maps doesn't have POV mode: you have to manually advance to the next turn
No "location sharing", people can't see where you are, and you can't see where they are
Only syncs one calendar
Email is just the body: PDF attachments have to be saved and opened in another app
Contact syncing breaks, so I had to manually transfer my core contacts
- Google's contacts for me is massive, I don't recognize most of these people
- Maybe this is actually a feature?
QR Code Reader is an app (has ads)
Podcast app has ads
MMS (group texts, or photos) can take a few minutes to arrive when the phone is closed. This may be a power saving issue.
Multimedia text messages must be opened to display them
200x320 screen resolution (smartphone is 2400x1080!)
Limited set of emoji on keyboard

Headphone jack doesn't detect speakers, only headphones
No way to automatically mute sounds during "quiet hours" (like, when you are asleep)
Predictive text input guesses one 4 means "g", not "I"
Will not play FLAC files
"Battery Full" notification can't be disabled
No international keyboard: goodbye, diacriticals!