Era 2 Engines
The general consensus seems to be that Lynx is the top engine for this era, whereas looks to me like Elephant is good for high delays goods, new goods would appear to follow in this category.
Looking at some numbers though it would actually appear like the Boar is much better option.
A quick comparison using a train efficiency calculator shows how previous assumptions are correct, Lynx is good for speed, so long journeys at any delay or short journey at little delay, however, Elephant vastly outperforms on short/medium hauls with high delay and even the fields on long journey where the waiting time is very high; however, it would appear that the Boar, whole being superior only on some corner cases, it's a better overall engine as it performs almost as good as both the other engines under their optimal conditions, making it better as an all-rounder.
More calculation required.