I believe that high-mounted headlights can light up the top of the nose, and that glare effects the crew's night vision.

Low-mounted headlights eliminate that glare, but the heat of the bulbs can be dangerous to crews on the front platform, let alone the hazard of accidentally looking right at one!

SP's 2nd-generation EMD hood units had headlights in the nose, and gyralights up between the number boards.

After SP quit using the gyralights in the latter half of the 1980's, their first order of GP60's came with headlights in the nose, but later orders (and the vast majority) of GP60's had them high between the number boards. Someone must of thought the higher position was better!