From what I understand, asbestos is far worse. Fiberglass causes irritation but that's about it. Asbestos, while it takes its time, will eventually cause mesothelioma and you really don't want that.
Fiberglass is very smooth compared to asbestos, at a microscopic level. That's what makes asbestos so bad - it gets in there and works its way further in, like a porcupine quill. Fiberglass is by no means healthy, but it's a fair bit less harmful.
I may have been misinformed, actually. Looking into it further, it seems like mechanical interference in cell division was ruled out. However, it seems there is some evidence that among other things, fibers beyond a certain length cause macrophages to essentially get destroyed trying to engulf them, which contributes to chronic inflammation, which is a big risk factor in many cancers
Fiberglass probably won't feel nice and might leave some permanent scars, but iirc, asbestos will do that and then some, but with particles so small that your body can never fully get rid of it