When comparing Taiga vs Notion, the Slant community recommends Notion for most people. In the question“What are the best cross-platform task apps?” Notion is ranked 10th while Taiga is ranked 30th. The most important reason people chose Notion is:
Even the right-click menus on the web are the same as the app.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Supports both Kanban and Scrum modes
User stories can be organized in both Kanban and Scrum task management systems.
Pro Free and open source
Taiga is licensed under GPL with source code available on GitHub.
Pro Simple to use
Pro Comprehensive Agile software development toolset
Taiga tries offering a complete Agile software development toolset. It includes complete solutions for issue tracking, videoconferencing, documentation (in the form of a wiki) and either a backlog or a Kanban board for managing user stories.
Pro Built-in issue tracking
Taiga has built-in issue tracking tools. The issues can be organized by user-defined type, severity, priority, creation date, assignee, creator, tags as well as filtered by subject. Taiga can also integrate with GitHub, GitLab and BitBucket.
Pro Built-in wiki
Each project has a wiki. It has Markdown support as well as a WYSIWYG editor.
Pro Built-in video conferencing tools
Integrates with either AppearIn or Talky to provide a video conferencing solution.
Pro Migration from RedMine
Pro Export/Import feature
You can extract all your data from one Taiga instance and move it to another one. You can read more here.
Pro Full-featured on desktop, mobile and web
Even the right-click menus on the web are the same as the app.
Pro Unlike anything else
One of the most complete applications one can use to build a personal dashboard (or professional) and migrate all other services to it. No more calendar, task, notes, financials, lists, writing and wiki apps, just Notion.
Pro Pages within pages within pages, to infinity
You can have a ridiculous amount of information within a single note. Look at how it works, you'll be surprised!
Pro Flexible contents storage and organization
You can upload files and embed online stuff in any hierarchical structure using pages, toggle lists, etc.
Pro Highly visual, with icons next to every new page and so on
This feature makes it very easy to find certain notes and such. And great for visual people as well. You could also add images as icons instead, if you like.
Pro Blocks offer incredible flexibility
The basic unit of organization in Notion is the block, which can be a chunk of text, an image, a bullet point, or even a link to another page. Each page consists of these blocks, which can be easily reorganized, moved to other pages, converted into other content types, or generally manipulated in many useful ways. Because of blocks, restructuring information in Notion is way easier than in any other wiki or notebook app.
Pro Does a great job with both notes and to-dos
To-dos in Notion aren't just dot point lists. You can drag and drop them into columns just like Trello (Kanban style), you can have sub-tasks, and you can easily mark things off as completed so they are no longer in your way. Notes are also powerful, with proper formatting and ways to manage and search for them, which makes it a great Evernote alternative.
Pro Cross platform
Works with Android, iOS, Windows, & Mac OSX.
Pro Awesome for wikis
You can easily start writing a bunch of web pages, share it with co-workers and choose whether to publicize or keep your contents private. It's also easy to hyperlink pages.
Pro Amazing view flexibility
You can create different views for a page's content and easily toggle between kanban, table, etc. (As long as the content is able to allow different views.)
Pro Quick and effective search
Just type in a word and you'll have results in no time at all.
Pro Attach files in tables
You can attach files in table cells, which is a feature missing in most spreadsheet-like applications.
Pro Great spreadsheet functionality
You can use calculation/formula, links, attachment, inter-referencing of data from other pages or tables, embed documents and images in the table cells.
Pro Renders Markdown Syntax
Add code blocks, Headers, bullet point, numbered lists, or To-Do boxes by typing using Markdown Syntax (instead of klunkily moving the mouse to formatting boxes)
Pro Less headaches when editing pages
Lets you restore your page to a past edit. Also works with sub-pages and databases. Though it is worth mentioning that it's a paid feature.
Cons
Con No Kanban metrics
Taiga is said to support Kanban but it does not generate any of the usual Kanban metrics (cycle time, lead time) or graph (Cumulated Flow Diagram).
Con Can be overwhelming at first
Taiga presents users with a lot of information and functionality right from the beginning with little guidance. Figuring how stuff works might take a bit.
Con Too much functionality for small projects
While it's possible to disable any unwanted features (modules), the amount of functionality that's present might be more than a small, short-term project needs.
Con Not very fast using native apps
Can take time if you're switching between lots of pages often as it needs to load the data each time
Con Not always very intuitive
Column filters are not that intuitive to apply.

Con No true backup
True backup can only exist if it's automated and easily recoverable. Else, it's just an outdated copy or useless scrambled data.
Con Designed with teams in mind, and less formatting than Evernote
Evernote may be more individual-oriented and has more formatting and such options available, but whether that affects you is down to personal preference. Try both and see which you prefer.

Con Not yet a new protocol, as it could be! (or could it?)
Think of scuttlebutt or email. the best Evernote alternative would be a "web 3.0" of sorts. Something that would be just a simple file added to a computer and automatically replicated to other computers along with a website and any company could easily pick up the concept and make their own hosting, including some awesome google drive/host of sorts.
