Thinking back to the 1970s when I first became a serious railroad enthusiast...
It seemed to me that the aesthetics of the locomotive designs from the two active and one recently departed U.S. builders seemed to match the personalities of the corporations.
---EMD had lots of straight lines (remember, by the time I got interested the standard EMD was a hood unit with a "Spartan" cab), and a roof line characterized by lots of identical modules: three to six 48" fans, depending on model. And GM was a big, modern, corporation, with (at that time!) a reputation for good management and a devotion to mass production.
---GE (remember, we're talking U-series here) had lots of smooth curves, and a touch of elegance: whatever you think of having the same fan cool the radiator when the engine is at full power and the dynamic brake grids when the engine is at reduced power, you gotta admit it's an ELEGANT idea. This was the company you'd go to if you wanted to find scientists!
---Alco... looked as if it was building locomotives from a box of mis-matched parts: think of all the ups and downs in the roof line of a C-636. (It reminded me of an old building-- Vermont farmhouses are the best example, but you could see similar achitectural effects in old, long-established, industrial sites: railroad shops, for example-- that had been repeatedly extended with additions built from available material with no unified architectural plan.) And Alco was the one of the three that was an old-line railroad supply company with 19th Century roots rather than a 20th C (yes, I know GE goes back to the 1890s, but you get the point) conglomerate.
So. Why was I an Alco fan? Why did I (then) think the C-636 was my favorite locomotive (even though the only one I ever actually SAW was shooting flames out of its exhaust stack)? Certainly it was the aesthetic and historical side of my railroad interest, not the rational side interested in efficiency (and environment-friendliness)!
((((PS:Since I'm now a ga-ga GE locomotive fan, I suppose I could say I'm a recovering Alco-haulic. ))))