Canvas or Poly Tarp? in Days of My Destiny

Just wandering what would be the best material to put under our camping tent, canvas or poly?

Any ideas or comments are most welcome.

I've been googling and there's lots to read on the topic but just thought I'd throw the question out there :)

The idea is to put the tarp under the tent for protection from all sorts of things, but especially sharp bindies that might go through the tent floor.

I could ask my husband but I don't want to as I'd like to surprise him with one.

Thanks in advance :)