You need to do a detailed analysis on the amount of energy and pollution generated by manufacturing and then repeatedly washing your reusable filter socks (lots of water which has been through a treatment plant plus beach which you end up dumping in a waterway plus electricity if you are using a washing machine plus wear on your washing machine which will thereby require replacement sooner and end up in a landfill) vs. the energy consumed and pollution by manufacturing the reef diapers which are more or less a thin paper like material. Only then can you legitimately ask this question. It is not clear to me which ultimately is 'worse' for the environment, and it likely depends on whether you prioritize conservation of energy and water vs minimizing landfill waste.
I would agree though that a biodegradable option would be nice, assuming it did not require more energy/material waste/etc to manufacture.
For comparison, see this link for a summary of a classic research paper describing a life cycle energy analysis on reusable vs. disposable cups: