In general, oxycodone is a bit stronger than hydrocodone -- but some people prefer hydrocodone. For me hydrocodone seems to have a "warmer" quality and oxycodone has a speedier quality, and hydrocodone feels better on my pain. But all commercial hydrocodone preparations contain Tylenol, which limits the dose, whereas most pure opioids due to not have a ceiling dose once tolerance to respiratory depression has been achieved.
hydrocodone Vicodin: contains 5 mg hydrocodone and 500 mg APAP (acetaminophen, aka Tylenol)
Vicodin ES: contains 7.5 mg hydrocodone and 750 mg APAP
Norco (10/325): contains 10 mg hydrocodone and 325 mg APAP
oxycodone Percocet: contains 5 mg oxycodone and 500 mg APAP
Oxy IR: contains 5 mg oxycodone (no APAP) -- IR stand for immediate release
Roxicodone 15 and 30: oxycodone that comes in 15 and 30 mg strengths (no APAP)
Oxycontin: Extended-release oxycodone (no APAP)
Generally in order of strength, it would go like this (from lesser to greater):
Vicodin, Percocet, Oxy IR (because it does not have Tylenol, can be prescribed in higher doses than Percocet), then Oxycontin.
-Wren
Edit to add: I was posting at same time as Steve (I kept the window open for a while) -- so sorry to duplicate info. Steve had really good advice, especially the bit about morphine being equipotent to hydrocodone -- that is true -- and of course, there will be individual preferences finding one "better" than the other -- that is relative.