When comparing Avalonia vs Microsoft Edge WebView2, the Slant community recommends Avalonia for most people. In the question“What are the best free controls for .NET?” Avalonia is ranked 4th while Microsoft Edge WebView2 is ranked 11th.
Specs
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Pros
Pro Open source
Pro UI designer plugin
A User Interface designer plugin for Visual Studio can be downloaded from the Visual Studio Marketplace.
Pro Cross-platform
WebView2 isn't just a Windows-only endeavor; the roadmap cites that cross-platform support is coming soon as a preview, which allows developers to code share across all platforms.
Pro Embeddable on Win32 applications
WebView2 is embeddable on Win32 applications, which allows them to enjoy the benefits of WebView even on traditional desktop applications.
Pro Compatible with older Windows versions
As WebView2 uses the same engine as Microsoft Edge and Chromium, it retains the same cross-platform experience that both browsers enjoy.
Pro Integrated within Windows
WebView2 is integrated on newer versions of Windows, including Windows 11, extensively used in Microsoft's own products.
Pro Free
Cons
Con Beta
Still in beta status.
Con Non-Greenfield deployments will require Microsoft Edge WebView2 Runtime installed
Applications that do not deploy as a greenfield application will require the Microsoft Edge WebView2 Runtime installed, which is installed alongside Microsoft Edge.
Con No Cross-platform support
The cross platform support for WebView2 is still in development which means code-sharing with other platforms if you're using WebView2 is not yet possible.