Not a surprising comment from the professional engineer. As pfx said the novelty goes away. That being said most engineers are more concerned with getting a comfortable, good unit that is a comfortable pleasant place to work and doesn't make the shift any harder than it needs to be. A unit with a clean cab and no subtle little faults is a favorite, the dirty unit with a laundry list of "not bad enough to get fixed" issues is despised. The later unit can turn a simple short job in to a nightmare. Additionally with multiple unit consists there are preferences on how they get set up, if you look at pictures of locomotive consists you will often see older units bracketed by newer ones. Often the lead unit had a nice cab while the second was, mechanically, the preferred unit. This could be because certain units did a better job in terms of real world performance while other units had a nicer ride and crew accommodations. As an example, the Bangor & Aroostook (BAR) had a habit of sticking a BL-2 in MU consists as the second engine as they tended to be "sure footed" but uncomfortable as a lead unit.