Whats better for under carpeting, felt or foam padding?

Question:

Answers:
On stairs I prefer a felt type pad (formerly known as hair and jute). Very good durability for a hard usage area such as stairs. 3/8ths of an inch thick should work very well over time without bottoming out like the lesser quality foam pads may. If you want a softer feel you could use a 3/8ths 8 to 10pound density "rebond" foam pad with good results.