I chose .NET Core because it finally let me work natively on my macOS and Linux machines but collaborate with coworkers using Windows. Devs use the devices that they feel most capable with.
Having services that can run without changes on Linux let us migrate to containerized deployments on Kubernetes without much effort. The performance we've gotten from small ASP.NET Core services running on Alpine images has been great.
While the versioning of SDK and libraries/meta packages/etc has been kind of nuts.. We also keep getting new features that are really valuable and easy to package into our services.
Just rolling out v3 of the WebJobs SDK which brought simpler DI, filters and more to our Async backend workers. Also preparing to run v2 of Functions in our Azure Kubernetes cluster with virtual-kubelet.
In the last year, the community has finally started heavily moving towards NETStandard 2.0 which has eliminated some of our last points of frustration -- not finding compatible clients/libraries/tools that we could use from .NET Core apps (and, funny enough our older .NET Framework apps too!).
We're all in on .NET Core now.