Scratches in slate?

I'm considering putting black slate on top of a new radiant heat system. I just went out to a tile place with whom I've done business before and been satisfied. The slate they had on display had numerous scratches, which were quite visible. They explained that kids playing on the display caused them. They also said that the scratches could be rubbed out using terry cloth or even paper towels. They had none of the former on hand and paper towels in fact did not rub the scratches out. They claimed their slate was of such high quality that sealing it was a waste of time; their slate in fact is not porous, and the sealant would just sit on top, becoming a maintenance issue.
Well, I have very boisterous kids too. Is scratching a common problem with slate? Can scratches in fact be rubbed out with terry cloth?
Also, they had two types of this slate--"natural" and "brushed." The latter was slightly polished, so felt silkier to the touch, than the rougher natural stone. My wife prefers the latter, but it seemed to me to scratch even easier. Does anyone have any experience with this?
Thanks,