Difficulty: Fanboi (if you don't know this without looking it up on the internet, then you play with Brio Trains).
The two major predecessor roads that merged to become NS did not have high-hood GP40-2's. And by all indications, NS did not buy any with high short hoods after the merger. So just how did they get a stable full of these relics of first-gen railroading?
As for talking points, Spartan Cab and high-hood locomotives are from my favorite era in railroading. Today's "school bus on rails" look of modern locomotives just doesn't convey the personality and power that the pre-comfort cab locomotives do. So why did railroads switch from high short hoods to chop noses? Well, if you read up on the internet (Bonjour!), that is a hotly contested question.
The fanbois who think they know better than anyone else have said that the noses were chopped for visibility reasons. Current and former railroaders say that is a myth. In one forum post I came across, it was mentioned that from the engineers seat, you can't see over the console equipment anyway if you are sitting down, so the configuration would only be useful if a low-flying plane were coming at you from the left side of the tracks. Also of note is a lot of the eastern railroads, where the second generation high hoods were prevalent, ran their locomotives with the long hood facing forward, so visibility wasn't an issue there either.
Another reason mentioned by the locomotive builders and buyers was that it was primarily a cost issue, with the low hood becoming standard issue and the high hood as an extra cost option. This didn't sit well (so it's read) with some train crews, who felt that their safety was being jeopardized over a few bucks worth of metal.
So what exactly was the high short nose on a locomotive used for? The most common use that pretty much every rail-fan knows of is the toilet. Of course, a high hood would have meant a bit more comfort for the user, as they could stand up to do their business. Collision protection was also touted as the reason for high hoods, but if those hoods were made out of the same thin gauge metal that the engine-end of the hood was made of, and with no extra bracing, I doubt it would have done much better than a low hood. Some railroads used the high hood for radio equipment or steam generators.
Any way you slice it, the years between the GP7 and the GP50 were the golden age for high-nose locomotives. If you see one today, you better get a photo quick. Norfolk Southern has chopped (or is chopping) and rebuilding it's fleet of GP40's, so the few that are left are either on short lines or in the scrap heap.