WP auto update is sort of nice in that you stay updated (but who the heck knows what will happen if you have one MySQL server and multiple www servers), except it means that your webroot is writable by PHP, which is not a great thing, because someone who finds an arbitrary file write issue before it's patched (or before auto update triggers) will be able to add their own files to your webroot -- weather that's defacement, malware installers, warez drops, bitcoin mining, shells for later; it's all pretty nasty.