The best feature is (for me anyway) it's fast and works consistently across all my devices. I've yet to have a reason to move to anything else.
If I was someone continually running into issues as some seem to continually have happen I might not feel that way, but I've been on the Catalina and iOS 13 betas and thankfully even with the betas didn't have issues.
EDIT: I did have earlier versions of the iOS betas duplicate draft messages. Which lead to confusion and double sending since at first glance it looked like like I hadn't sent a message in drafts; once I figured out what was going on I would just check my sent to make sure I sent it before deleting the dupe in drafts. At least it wasn't a data loss bug.
If I was someone continually running into issues as some seem to continually have happen I might not feel that way, but I've been on the Catalina and iOS 13 betas and thankfully even with the betas didn't have issues.
EDIT: I did have earlier versions of the iOS betas duplicate draft messages. Which lead to confusion and double sending since at first glance it looked like like I hadn't sent a message in drafts; once I figured out what was going on I would just check my sent to make sure I sent it before deleting the dupe in drafts. At least it wasn't a data loss bug.