I reckon Sam is the definition of p4p..I think he is the benchmark for the term and probably had the greatest p4p achievements out of any fighter in history. As for who is the greater fighter....Ive seen arguments that put either higher, they are pretty close in this regard. I personally have Sam higher but I feel both are a lock for top 10.
Langford. The man could do it all - Power, speed, defense, footwork, stamina, conditioning, heart. I feel he is the greatest fighter who ever lived, not to mention the most avoided. No disrespect whatsoever to Greb, who is easily top ten all time.