"Disposable" does not equal "biodegradable" even in the world of tea filters. The new tea filters I got are actually made out of polyethylene/polypropylene. So I have to rip them apart after use, sprinkle the tea leaves into the compostable trash and throw the used filter in non-recycling trash (or can I recycle them as plastic?). This is quite inconvenient compared to the usual biodegradable filters that I can just throw straight into the compostable trash. | 
It seems to me that steel tea-eggs are better for the environment, more convenient, and gives as good or better/healthier tea.
Convenience is the biggest factor. I really liked the 'single-sort recycling' system they had in Madison last I was there. Glass, plastic, paper and cardboard is just tossed in the same container and sorted out at the recycling facility. More people will recycle if you make it easy for them. But they didn't have any composting service.
If I lived in an area where I couldn't do my own compost, these filters would be great.
Obviously, re-usable is the best for the environment. But those all require cleaning between each use. I've grown too used to the convenience of just tossing the entire filter in the compost.