Although the pressed coco fiber panels are extremely expensive, they do not break down quickly, sustain epiphytes such as bromeliads, hold moisture, and although not as attractive as cork bark for decorative purposes, you can use them behind pieces of cork bark if you want a more attractive surface to begin with. The plants you attach to them won't rot off and will reproduce readily upon them, as will stray fern, mushroom and moss spores. The tree fern roots are more loose and I have found them to be less useful for attaching to glass. The coco fiber panels can be siliconed to the back of your vivarium, either on top of a cheaper and thinner coconut fiber matting, if you want to save costs by spacing them around for individual epiphytes, or directly onto the glass. I really like them. The fern root (osmunda??) is loose and tangly. It has it's uses in a pot of orchids or as part of a terrarium substrate, but it is not very good for a terrarium backing where you are placing epiphytes against a glass background. I have it in my imitator tank around some orchids, but not as a backing to hold epiphytes like bromeliads. The frogs burrow in it and have never been caught up into it as I feared they might. At this time, a year later, I'm seeing a couple of new shoots of one of the orchids coming up through it. The frogs have laid eggs behind it against the glass.
So the answer may be that it is not "either or" but both suit different purposes, depending upon what you are planning to do.
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Patty
Pahsimeroi, Idaho
4 D. auratus blue
3 D. galactonotus pumpkin orange splash back
5 D. imitator
4 D. leukomelas
4 D. pumilio Bastimentos
4 D. fantasticus pending