Joe and Maria writes:

Is there any disadvantage to porcelain, such as being more fragile?

No. Porcelain is harder and stronger. Narrow scrsps (the size of a
pencil) can be hard to snap in your hand. The disadvantage is
(potentially) the cost, since it is fired longer.

I have read that all tile boxes are stamped with a rating of the amount
/degree of freeze thaw cycles they have been tested for.

It would seem that freezing is something they either take or don't, based
on water absorption.

Most of the tile at Home Depot or Lowes doesn't have proper technical
ratings like WA. Some of it does, and whether it does or not seems to have
no correspondence to its cost.