Is Microsoft still working on both products? Has development on TFS been dropped in favour of VSTS?
For context, we are using TFS right now and VSTS clearly has better integration. Specifically with Microsoft Teams and ZenDesk which is important to getting our workflow process in a more manageable state. However, VSTS doesn't have anywhere near the configuration or reporting that we require.
Will either product eventually have the full feature set or will we have to choose and build our own integrations or reporting?
Now Azure DevOps and Azure DevOps Server, but the rest of the story remains intact.
Visual Studio Team Services (VSTS) and Team Foundation Server (TFS) are based on the same codebase. VSTS is deployed to the cloud every 3 weeks or faster. TFS has received a major upgrade yearly (2015, 2017, 2018) and a major update pack every 3 to 4 months (2015.0-3, 2017.0-3, 2018.0-1).
Most new features are released to Visual Studio Team Services first and are integrated into Team Foundation Server with a bit of a delay. Some features are available in VSTS which depend on cloud resources, so they're not likely to move to TFS anytime soon.
With regards to reporting, this has been a bit of an Achilles' heel of VSTS. It has never had the Report Server and Analysis Cube capabilities of TFS. It does offer integration with PowerBI and that integration is quickly getting better.
You can see the overview of feature availability between cloud (VSTS) and server (TFS) on the Feature Timeline, as you can see a lot of new things happening, most of them are hitting VSTS first.
Microsoft offers a support lifecycle for Team Foundation Server and currently, it looks like Microsoft won't abandon their on-premise customers anytime soon. TFS 2018 has an extended support lifecycle all the way to 2028:
Products Released Lifecycle Start Date Mainstream Support End Date Extended Support End Date Service Pack Support End Date Notes
Visual Studio Team Foundation Server 2018 11/15/2017 1/10/2023 1/11/2028