If you can do what you want to do with Termux, use Termux. It's quite battle-tested at this point, has better UX, fewer bugs (eg. no VPN issues), and is more efficient than the new built-in VM. Want to do SSH stuff or Ollama or compile code, Termux is great.
However, the native VM has more potential. It can run more or less any Debian package, and it has native GUI mode with (on Pixel 10s) hardware acceleration, instead of going through VNC tunneling. So I would choose it if I had external keyboard/mouse/monitor(s) and wanted to run Krita or DaVinci Resolve or other big GUI tools.