When comparing Discourse + Digital Ocean vs Vanilla, the Slant community recommends Discourse + Digital Ocean for most people. In the question“What are the best hosted forum platforms?” Discourse + Digital Ocean is ranked 1st while Vanilla is ranked 2nd. The most important reason people chose Discourse + Digital Ocean is:
Discourse can upgrade itself with one click in the admin panel. Not the same can be said about MyBB, or most other forums.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Easy one-click upgrade
Discourse can upgrade itself with one click in the admin panel. Not the same can be said about MyBB, or most other forums.
Pro Discussions can be organized in categories and tagged
Discussions can be tagged with an arbitrary number of tags, separately from categories. Categories are hierarchical and don't scale; tags do.
Pro Advanced JavaScript app
Runs in modern browsers and works identically on desktop and tablet and smartphone without the need for a native app.
Pro Has a built-in immune system from trolls, spammers and bad actors
Discourse has a simple user trust system that makes moderating the forum a lot easier. Users gain more permissions as they gain more trust, which limits the amount of damage spammers and trolls can do. Discourse co-founder Jeff Atwood also founded StackExchange, which is the gold standard for gamification/moderation systems so you can also expect Discourse to get better and better at moderation.
Pro Modern & polished UI/UX with lots of great smaller features
The best feature is its design: discourse is designed to aid in the creation of high quality online conversations. Flat discussions with well implemented quoting systems, expandable/collapsible replies, infinite scroll, clean UI and many more features come together to form a highly polished forum experience that makes legacy forums show their age.
Pro 100% free and fully open source
Discourse is powered by Ruby on Rails, Ember.js, PostgreSQL and Redis. The code is licensed under GPL and available on GitHub.

Pro Free and open source
Vanilla is a free PHP+MySQL application that's licensed under GPLv2 with source code available on GitHub.

Pro Importer from many other forums
Vanilla Porter can import posts (comments), threads (discussions), users, categories, roles and passwords (hashed) from most other forum software: bbPress, Drupal, MyBB, NoteBB, phpBB, PunBB, SimpleMachines 1&2, Toast, UserVoice, vBulletin, Xenforo, YAF.NET and others. Some importers support avatars, attachments, signatures, and PMs. A few support tags and user notes.
Imports aren't flawless, but they do most of the work.

Pro Easy setup
Vanilla is a MySQL + PHP app and can be set up very easily.
Pro Simple forum software
lightweight Internet forum package
Embeddable forums
Import from other forums

Pro Discussions can be organized in categories and tagged
Discussions can be tagged with an arbitrary number of tags, separately from categories. Categories are hierarchical and don't scale; tags do.

Pro Fast
PHP may not be the most modern language, but Vanilla is fast.
Pro Hosted and self-hosted options
Pro Single Sign On
Ability to sign in with another system to your forum
Pro Deep integration with WordPress
Use SSO with your WordPress site, adds recent discussions widgets and best of all have comments also create discussions in your forum.
Cons
Con No themes beyond changing colors
Discourse doesn't have a themes ecosystem. All you can do is change the colors.

Con Poor search, unless using Sphinx
The default search that comes with Vanilla produces poor results because it uses MySQL. One needs to investigate integrating with Sphinx for much better results.
Con Vanilla Cloud offering is expensive for bigger communities
The commercial options of other software providers are generally better value-for-money. Vanilla is a cheaper option if you commit to self-hosting.

Con No post edit history
Old versions of a post are only visible to admins, which may lead to a credibility problem. The amount of time during which users can edit their posts is configurable from a few minutes to indefinitely.
Con Templating could be better
It is difficult to customise Vanilla in a way where it can be source controlled. This may be a benefit for communities who just want to get up and running, but is a drawback for developers.
Con No sitemap for discussion
Even sitemap plugin cannot add discussion in xml file.
