I hope that more experienced members will answer your question about preference, since I have never used repti-bark before. However, my guess is that it would be fine to do so.
Coco coir looks similar to repti-bark, and holds humidity pretty well. I have to dry the coco coir out after adding water, or else it spikes the humidity to 80-90% right away. It would depend on where you live though and the RH in your house. The humidity in my place stays around 50% all of the time.
I like coco coir's natural look in the vivarium. I hope this helps.