"These trains are region specific and you may get double or triple locks when your fleet in that region is weak. Event locos start out more powerful, extend farther, and aren't region specific so you won't get locked as badly."
This is pretty muddled. All trai--^W<coughcough> sorry, 'locos' are region-specific: whatever region you get them in, you only use them on the corresponding jobs. There's really only a 'chrome' distinction: the epics in Canada look different from the epics in the Netherlands, but behave the same, whereas you could have the same Construction Event epic in either, depending on your gameplay. But once it's in Canada, it cant get out again. (Nooooooooooooooo....)
The advantage is essentially the locks one, but that's pretty substantial. The most usual bluetop job is a double-lock: that become a single-lock with ETO. Events are a mixture of single-, double-, and triple-locks: now all singles. Story jobs are immune (I think?). We suspect there might in some cases be a job-size effect, but that's monstrously hard to pin down here. But better to just have a definition here, and maybe a link, rather than a lengthy discussion.
Oh, that reminds me of one other headword for you: 'commercial job' (Pixelese), 'blue job' or 'bluetop job' (forumspeak), occasionally also 'regional job' (which IMO is confusing at any speed -- aren't they all?). The normcore default jobs that are unnumberedly generated infinitely, and aren't part of an event, competition, storyline, or region-unlock task. (And easy/medium/hard subtypes.)