Miniconda is faster (I prefer it, personally)...

...but Miniconda and Anaconda are the same package manager, the difference is that Anaconda comes batteries-inclused with a ton of common packages.

The reason Miniconda is faster isn't the solver, it's because it doesn't have 250 packages to go through the long checking process on.

If you have a large, complex environment in Miniconda, that environment will get slower and slower to resolve over time.