They have different use cases. uv is meant to be the singular tool for managing Python packages and dependencies, replacing pip, virtualenv, and pip-tools. Conda is for more general-purpose environment management, not just Python. If you're doing something with Node or R, uv won't work at all because it's only for Python.
uv's biggest advantage is speed. It claims a 10-100x performance speedup over pip and Conda [1]. uv can also manage python versions and supports using Python scripts as executables via inline dependencies [2].
But Conda is better for non-Python usage and is more mature, especially for data science related uses.
[1]: https://github.com/astral-sh/uv/blob/main/BENCHMARKS.md [2]: https://docs.astral.sh/uv/#scripts