Lots of people will have their favorite substrate, mine is newspaper because I'm practical and cheap, lol. Plus my enclosure is basic.
If you've got a display enclosure, I'd go for the coir peat stuff, you can then just take out the wet/dirty stuff and replace it, or Kritters crumble (safe for reptiles, Petstock has it) , so same deal, youre' only taking out the stuff that is wet/dirty.
Marine carpet would be okay, but if you've got lots of decorations on the floor of your enclosure, then you're having to move a whole lot of stuff to get it out, wash and replace.