I agree that it's personal and average to heavy riders need steel rails. I've seen average riders who are fast (pull more G forces) break saddles and rails. The saddle break by developing cracks in the middle and sag more than they are designed to.
An old teammate of mine loved one particular Specialized saddle. The saddle would crack in the middle after a day or two of riding on the track. The shop that sponsored us was a Specialized dealer so he got a new saddle over the counter no questions asked each time, but it was still a pain in the butt (pun intended).
Saddles and seatposts are very important. They are the foundation of everything. As one owner of a tri shop that handled the most expensive bikes for his tri customers put it, "Trackies are 'The Princess and the Pea' when it comes to their bike fits."