Welcome to the forum Va4rizor, great question. I suppose the short answer is that we don't really know as there is are no long term studies for either.
But I will say that silica wicks (for the most part) are impossible to burn at the temperatures we use - if you want proof, take a bic lighter to some silica and see. So long as you keep your cotton moist, it won't burn either.
I had a similar question a few months back and found an excellent discussion about silica and the dangers (or lack of) associated with it. Let me see if I can find it.
EDIT -
This is a much older
thread but I can't find the discussion I was looking for. It's 11 pages, some of it is silly bickering to be honest, but there is some good information in there.
This has been a question asked a lot on the forums and I suppose the answer is, we don't know if
vaping in general is as safe as we may think - although all initial indications are that it is - and so that would include the long term safety of the wicking materials we are using.
As anything else, I highly suggest you do some research and then make your own informed decision at your own risk ( I suppose you started it by asking this question

)
Finally there is a
medical-research forum right here in ECF that you can look at. I think you'll need 15 posts before you can actually post in there, but you can review the articles.