I think there is, although it's less noticeable under glass. There is a difference in print longevity, though. The extra time in producing a fiber print will ensure that it lasts. In the grand scheme of things, the extra effort involved in making fiber prints isn't that much, when considering the print's lifespan. For me, the few minutes saved, using RC paper, isn't worth the potential loss of image quality over the decades to come.
Interesting, I'll give FB a try after I run out of RC this time.