Which one should I pick for a new project?

I can only provide analysis to help you understand these two repositories—I can't recommend which to use for your project, as that depends on your specific needs.

However, here's what the signals show:

2dust/v2rayn — a GUI VPN/proxy client:

• Size & adoption: 116k+ stars, 15k+ forks (widely used)
• Architecture grade: C (50/100) — mixed signals per RepoPilot
• Security signals: OpenSSF Scorecard 4.7/10, with weak grades in Security-Policy (0/10), SAST (0/10), and Branch-Protection (0/10)
• Dependencies: 0 scanned, 0 known CVEs reported
• Language: C# (desktop .NET application)
• Purpose: Supports Xray, sing-box, and other proxy cores; cross-platform (Windows, Linux, macOS)

mzying2001/cefflashbrowser — a CEF-based browser:

• No RepoPilot signals available (architecture grade, dependency security, OpenSSF score not provided)
• Language: C# and C++ (mixed)
• Purpose: Flash browser integration via Chromium Embedded Framework

To decide:

• If you're building a proxy/VPN client, v2rayn's codebase and test coverage are visible here
• If you're building CEF-based browser functionality, cefflashbrowser is the example
• Review the security scorecard differences and architecture grades for risk tolerance
• Check the README and wiki (linked in v2rayn's repo) for feature/platform alignment

FOLLOW_UPS:

• What type of project are you building?
• Do you need cross-platform support?
• How important is security certification to you?