I agree with this disagreement.

I have a Swift on my road bike that's been on there for a little over a year, and just put a Swallow on my fixed. The Swallow is hard, but it's much better on my taint than the stock saddle that came with my bike (San Marco Ponza). However, these are the only two (unsprung) saddles I can use from Brooks because they're the only two with the long rails. I had a B17 for a bit on my road bike, but couldn't get it in a comfortable position no matter how hard I tried. Turned out the rails were just too short for my tastes.