I made a long explanation about it a long time ago but can’t remember everything I said. Basically, BackupWordpress has all the features I need for free and doesn’t nag me at all like UpDraft.
Off the top of my head, Updraft: 1) doesn’t back up the entire root directory unless you pay for premium (so it misses my secret directories or files that I or clients may have placed in unconventional locations), 2) leaves orphan data in database when you uninstall it (probably trying to preserve settings, etc), 3) just annoying GUI that isn’t as easy to use as BWP in my opinion, 4) feels bloated to me 5) nags me to pay for premium.
I absolutely hate it, but am fully aware and respect many developers who swear by UpDraft and trash BackupWordPress for “just doesn’t work, keeps spinning forever”. I feel BackupWordPress can be finicky especially on shared hosts where it sometimes runs out of memory but when it works, man I love it so much more.
I also feel Updraft is great if you like to back things up in bits and pieces and restore them bits and pieces. It’s great for modular backups and granular control, but horrible for if you just want a simple ‘back everything up’ option.