I don't know who told you that VaultWiki is "only sorta integrated with XenForo". VaultWiki is a XenForo add-on, not a bridge to external software. This means the user accounts, search, etc is the same system. That might be a plus or minus for you, depending on your needs.
Wiki content shows up in XenForo search.
New wiki updates show up in XenForo's What's New, profile activity, user alerts, etc.
Wiki contribution counters appear on the user's profile and can be used for trophies, forum-notice criteria, etc.
The wiki editor is the same editor as regular forum posts, supporting the same BB-Codes as forum posts (and then some).
You can use XenForo's bookmarks on wiki content.
You can use XenForo's Like/Reaction functionality on wiki content.
You can have wiki content and edits require approval, and you can give that approval using XenForo's approval queue.
There are a number of wiki-related widgets that you can use as XenForo widgets in its sidenav, sidebar, etc.
As
@expanserpb noted, VaultWiki allows auto-linking of terms.
Unlike XWiki, VaultWiki is not namespaced. This means that kinds of wiki content (categories, etc) are not explicitly tied to any one title prefix (such as Category:CategoryName in XWiki). VaultWiki is organized in areas, which is a hierarchy like forums, and allows you to put custom permissions for the wiki based on the user's XenForo usergroups.
There are really way too many features and options to try to talk about here.
However, since you asked about it, VaultWiki does not currently provide a way to automatically put discussions in specific forums. They are a separate comments section under the content or on a new tab, like comments on a user's profile are not in the forums. However, you can sort of do this with a patchwork of BB-Codes linking to unique forums, and/or by using the wiki integration positions available in forums and threads (create a thread and insert the wiki content above it). For a more streamlined way to connect forum threads as a discussion list, there are plans to add that capability in the next branch (that could be a long time so if it's a deal breaker then maybe XWiki is for you).