'Depend upon' or 'depend on' [duplicate]

NOAD:

The preposition ‘upon’ has the same core meaning as the preposition ‘on’. ‘Upon’ is sometimes more formal than ‘on’, however, and is preferred in the phrases: once upon a time and upon my word, and in uses such as: row upon row of seats and Christmas is almost upon us.

There is no other difference than that.

Grammatically there is no difference.

Style and usage? It is one of the "nicer" selections to have to make, as you can choose based on:

a: It is better to your ear,(1)

Or:

b: It is better targeted at your readership,

Or:

c: A combination of a and b.

(1) Italian has a word ("orecchiabile") for which the closest English translation is "palatable to the ear". Given that English is, shall we say, an "illegitimate" language, whose parentage is not strictly defined, I think that we should either steal the word (to add to the list of other words we've stolen), or create one that means the same thing.