Why would I choose Space over Upsource, YouTrack and TeamCity? Follow

Space is an Integrated Team Environment which includes not only software development oriented tools such as code review, issue tracking and continuous integration, but also team directory, calendars, HR, knowledge base, messaging, and many other features for various roles in a company. It is a complete solution that can be hosted on-site or as a service and requires little to no integration with other software products that have similar functionality, and yet does provide support for 3rd party products.

Upsource, YouTrack and TeamCity, while they can be integrated together, are also standalone products that can be used with many different solutions.