How does this product compare to using cerium on felt? ease of use? efficiency? results?

The Brown Polpur wheel will polish with just water as the cerium is built into the wheel. It won't polish as quickly as felt and cerium slurry but it is far cleaner and easier to use than felt and cerim slurry. It also does not build up as much heat on the glass while polsihing. The drawback is that it does tend to wear down faster than the grit versions of the Polpur wheels.