The plates are cleared, the candles have burned down to a serious stub, and someone at the table says the word that defines autumn eating: digestif. Out comes the brandy, and with it the small confusion that has haunted dinner tables for two centuries. Cognac or Armagnac? They sound like cousins, they share a country and a grape, and they sit side by side on every back bar looking faintly identical. They are not. One is the tailored suit. The other turns up in a good tweed jacket that smells faintly of woodsmoke, and by the end of the night it is usually the one you remember.

Both are French brandy, which is to say both begin life as thin, sharp white wine and end it as something golden and slow that nobody would dream of drinking before the clocks change. Both are distilled from grapes, aged in oak, and built for the quiet end of an evening. After that they part company almost entirely. Where they grow, how they are made and the character each brings to the glass could hardly be more different, and once you can tell them apart you will never again nod blankly at the trolley.

Two Brandies, One Country

Draw a rough line across the south-west of France and you have found both their homes. Cognac comes from the Charente, up towards the Atlantic above Bordeaux, a region of chalk and easy commerce that has been shipping its brandy to the world since the seventeenth century. Armagnac comes from Gascony, the deep rural south-west of d'Artagnan and foie gras and village rugby, inland and a little untamed, between the Adour and the Garonne. Cognac grew up as an export business. Armagnac grew up on the farm. You can taste that difference in temperament before you taste anything at all.

Cognac: The Polished One

Cognac is the one the world already knows by name. It is distilled twice, patiently, in small copper pot stills, a method that strips the spirit back and hands you something clean, round and beautifully behaved. The great houses, Hennessy, Rémy Martin, Martell and Courvoisier, are masters of the blend, marrying spirits of different ages and villages into a house style you can rely on from one year to the next. That is what the letters are telling you: VS for the youngest, VSOP for a little more age, XO for serious maturity. A good Cognac is silk. Dried apricot, vanilla, a warm hum of oak, nothing out of place. If you want the full argument for treating it properly rather than warming it over a candle like a film villain, we made the case in our guide to Cognac.

Armagnac: The Wild One

Armagnac is the older soul, and the more characterful by a distance. It is, by most accounts, the oldest brandy still made in France; the lore runs back to 1310 and a Gascon prior who set down forty virtues of the stuff, which was either early medicine or an extremely good excuse. The crucial difference is in the making. Armagnac is usually distilled only once, in a tall column still of its own design, the alambic armagnacais, which leaves the spirit at a lower strength and a higher flavour. Nothing is polished away. What you get is richer, rounder and handsomely rustic: prune and dried fig, toffee, black pepper, old leather, sometimes a waft of the Gascon countryside itself.

It leans on the same workhorse grape as Cognac, Ugni Blanc, with Baco, Folle Blanche and Colombard along for the ride, across three zones worth knowing. Bas-Armagnac, on sandy soils, makes the most prized and perfumed; Ténarèze brings grip and structure; Haut-Armagnac is the smallest player of the three. And here is the detail that turns drinkers evangelical: because production is small and farm-based, Armagnac is bottled by the single vintage far more readily than Cognac ever is. You can buy the year you were born, the year you married, the year the century turned. Domaine d'Aurensan's 1998 Millésime is exactly that, a snapshot of one Gascon harvest left to grow old in a barrel while the rest of us got on with things.

So, Which One Tonight?

Match the brandy to the mood. If you want polish, reassurance and a drink that behaves impeccably in front of guests, pour Cognac. If you want character, a story and a spirit that tastes of a particular place in a particular year, pour Armagnac. Price rarely settles it: both run from the sensible to the frankly silly, and a very good bottle of either can be had for less than a decent restaurant round. The real question is what you are in the mood to taste, the house style or the handprint.

If you would like to settle the matter the only sensible way, by trying them against each other, start with one of each. A grande-marque Cognac that shows exactly why the style conquered the world, and a single-vintage Armagnac that shows exactly why the cognoscenti keep quietly drifting the other way. Pour them side by side after dinner and let your own palate cast the deciding vote.

Take the Cognac first, while your palate is fresh, and let its polish set the baseline. Then sit with the Armagnac as the room goes quiet. One is a beautifully made drink. The other is a place in a glass, and by the second sip you will understand why Gascony has never felt the need to raise its voice.

The Autumn Case for Armagnac

There is a reason brandy belongs to this stretch of the calendar. As the nights draw in, the stills themselves wake up. From late October through the winter the alambics fire across Gascony for the new season's distillation, an event the region turns into a travelling festival, the Flamme de l'Armagnac, with tastings held beside the running still. It is the most seasonal spirit there is, made in the cold, for the cold. A measure of it beside a fire, or just beside an honest radiator and a bowl of walnuts, is one of the quiet pleasures of a British autumn.

If you would rather stay in the orchard than the vineyard, Gascony's northern neighbour offers Calvados, the apple brandy of Normandy, which does much the same warming work with a note of baked orchard fruit in place of the dried. But for pure autumn character the Gascon bottle is hard to beat. Cognac will always be the safe and splendid choice. Armagnac is the one worth being a little braver for.

So the next time the trolley arrives and someone asks the eternal question, you will have your answer ready. Cognac if the evening wants smoothing over. Armagnac if it wants remembering. Pour the wild one as the first proper cold night sets in, and raise a glass to the alambics burning away in a field in Gascony, doing in the dark exactly what they have done for seven hundred years.