It is very difficult, if not impossible, to distinguish between these terms in English wine-speak, as a glance at, say, the English edition of Gambero Rosso's annual wine guide will show. And the best glos, by Giles Watson, gives "fragrance, aroma" for both. Whether you use one or the other, or "scent, hint, nuance, suggestion, impression," etc., depends more on your ear and style than on a supposedly-objective definition--particularly definitions in Italian, which will give you NO guidance to the words' use in English..

A standard oenological term in English for this sort of things.
Lookitup!

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Note added at 1 hr (2009-07-14 22:14:10 GMT)
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sorry, I forgot, the twit! Nose is for "aroma". Profumo would be "fragrance" or, very often, "accent".

The distinction between aroma and bouquet is one of age as explained in the glossary quoted below:

aroma: Aroma is the smell of a young wine before it has had sufficient time to develop nuances of smell that are then called its bouquet. The word aroma is commonly used tohttp://www.proz.com/kudoz/3354454#marker_submit mean the smell of a relatively young, unevolved wine.

nose: The general smell and aroma of a wine as sensed through one's nose and olfactory senses is often called the wine's nose.

bouquet: As a wine's aroma becomes more developed from bottle aging, the aroma is transformed into a bouquet that is hopefully more than just the smell of the grape.

nose: The general smell and aroma of a wine as sensed through one's nose and olfactory senses is often called the wine's nose.

So as your case is talking about a single vermouth, I would go for nose and bouquet.