They will offer no benefit over sand. The filtration claims are fairly bogus since water is not forced through a solid mass of these, they will break down within a couple seasons while sand can last forever, and I don't understand how something that has to be manufactured and replaced regularly can be considered more environmental than sand.
The best thing for a sand filter is sand. If you feel the need for better filtration then a cartridge filter will do the job, but water clarity is largely a function of water chemistry. Keep the water balanced to TFPC spec and any filter can keep it clear.