Alright, nothing's getting through. I suppose the average railfan will always believe that steam locomotives were harder on the track than diesels (not true in the case of properly counterbalanced rods and high drivered locos - traction motors actually were more likely to excert lateral forces on the rail due to the lower center of gravity). I suppose the average railfan will always believe that a new steam engine was more expensive than an equivalently powered diesel - again, not true. The new diesels were much more expensive on a hp equivalent basis, and had a nominal (read: pre-overhaul) lifespan roughly one third that of steam.

The one huge factor in favor of diesels at that time was the price of diesel fuel relative to coal.