This is similar to the relation between “while” and “whilst”, or between “amid” and “amidst”.
As with "whilst", "amongst" is:
chiefly British
"while using whilst runs the risk of sounding pretentious, it can sometimes add a literary or ironically formal note to a piece of writing" [American Heritage Guide]
"The general consensus among scholars of English is that whilst is an unnecessary and archaic word whose primary usage is by Britons who prefer what they perceive as a more 'noble' word" [Strunk and White]
recommended against by Times Online Style Guide: "amid, not amidst; similarly among, not amongst", by the Guardian Style Guide: "among not amongst", and by [Hansard Association of Canada]: "among (no -st)". And some Tameri Guide says: "among / amongst - In American English use among to mean within a group. Amongst is antiquated for in the middle of a situation or gathering."
Anyway, the summary seems to be that "amongst" is slightly pretentious (or "distinguished" as you say), but is common in Britain, and its meaning is almost identical.
A couple of colleagues and I have been going through some Google NGrams. At first it seems quite conclusive that plundering is a far more sea worthy activity than pillaging, and plundering is certainly the more pirately thing to do:
In an actual example: British critic: and quarterly theological review, Volume 16 (pp. 516 to 518), they appear to use pillage and plunder interchangeably as nouns, but only plunder as a verb. This seems fitting for water-borne criminality.
In this discourse of plunder (page 2) pillage is said to be something that makes up plundering.
However, the further I read into the samples provided by the Google book search, it seems that pillage and plunder can be used interchangeably, it's just that plunder is a far more popular word.
In fact, although it is a much rarer occurrence than "pirates plundered", "pirates pillaged" does appear in literature. Some examples:
Outside of buccaneering, there is a lot of synonymous usage of plunder and pillage - here are some examples:
In a text about the history of English government, on page 94 they write:
Commercial plunder, however, was to be more destructive than military pillage
On page 554 of The new encyclopædia; or, Universal dictionary of arts and sciences they define Pillage by using plunder. An later on page 687 they define plunder using pillage.
There seems to be no difference in the meaning of the two words in The works of the Right Honourable Edmund Burke, Volume 7 on pages 408 and 410
Again I find the same in "The Forum, Volume 17" (plunder, pillage)
So, in conclusion, it seems that plundering and pillaging are the same thing.
Best Answer
The American Heritage Dictionary of the English Language gives four definitions of role, the first of which is
while the other three definitions (related to functions or characteristic behaviour) do not offer rôle. So for some people the circumflex indicates a particular meaning. Not for me.