Should I follow English conventions, or write what sounds better?

Solution 1:

Your best option would be to check a dictionary as it will usually have a note to clarify such ambiguities.

ODO's entry for data notes:

In Latin, data is the plural of datum and, historically and in specialized scientific fields, it is also treated as a plural in English, taking a plural verb, as in the data were collected and classified. In modern non-scientific use, however, it is generally not treated as a plural. Instead, it is treated as a mass noun, similar to a word like information, which takes a singular verb. Sentences such as data was collected over a number of years are now widely accepted in standard English.

The data/datum question has been covered on ELU before.

Similarly, the entry for hoi polloi carries the following note:

1 To those in the know, hoi is the Greek word for the definite article the (nominative masculine plural); the phrase hoi polloi thus translates as ‘the many’. This knowledge has led some traditionalists to insist that hoi polloi should not be used in English with the, since that would be to state the word the twice. Such arguments miss the point: once established in English, expressions such as hoi polloi are treated as a fixed unit and are subject to the rules and conventions of English. Evidence shows that use with the has now become an accepted part of standard English usage.

Solution 2:

This is a fairly fundamental challenge in the way we say what we say. Unquestionably, "data" is plural. Just as unquestionably, it is used as singular in almost all instances.

In such cases, I generally try to apply the simple question of whether the "incorrect" usage confuses the picture, or hampers clarity of expression. My answer for "data" would be that we really have almost no use for the singular "datum," and it seems well understood, with no real potential for confusion, what "data" means.

So I would go with the common usage, but would not fault anyone for using the "correct" one.