Core 2.0 is 20% faster than its previous version .NET Core 1.0.
Core – Primitives, Collections, Reflection, Interop, Linq
Serialization – BinaryFormatter, Data Contract, XML
Threading – Threads, Thread Pool, Tasks
Networking – Sockets, HTTP, Mail, WebSockets
IO – Files, Compression, MMF
.NET Core 1.x on macOS required the OpenSSL toolkit's cryptographic library. .NET Core 2.0 uses the Apple cryptographic libraries and doesn't require OpenSSL, so you no longer need to install it.
.NET Core 2.0 offers a single Linux implementation that works on multiple Linux distributions. .NET Core 1.x required that you download a distribution-specific Linux implementation.