“When you use Signal, your data is stored in encrypted form on your devices. The only information that is stored on the Signal servers for each account is the phone number you registered with, the date and time you joined the service, and the date you last logged on.”
I abandoned Whatsapp several years ago and since then have used Signal nearly every day (to keep in touch with a handful of friends), have had a recurring monthly donation set up for a couple of years now.
One on the one hand there’s the privacy, but what clinched it for me originally was the ability to seamlessly switch from my tablet to the cellphone to the desktop, all Apple. Signal was (and probably still is) better at this than Whatsapp.