And, a little FYI for folks who don't know the difference between cognac and scotch:
Cognac is a type of brandy, just like Bordeaux is a type of wine. To be classified as a cognac (and not just "brandy"), certain grapes must be used, certain wooden barrels must be used, etc. But none of those legal requirements exist outside of France (and treaty countries), and in the US, "cognac" could easily refer to a style of brandy, just like a wine labeled a bordeaux in the US doesn't actually have to be created in the Bordeaux region of France--any more than a champagne in the US has to have been created in the Campagne region,
though this is changing. Now that US wine regions are starting to get their own reputations, we are becoming more concerned, as a nation, about respecting those same reputations from foreign countries.
Note that all of the scotches in my tasting pack are all authentic Scotland scotches, and all of the cognacs are all authentic French cognacs.
Both types of liquor are distillations. Scotch is made with grains, cognac/brandy is made with grapes. So basically scotch is distilled beer, while cognac is distilled wine.
Both are then aged in barrels, which means that there will be quite a few tasting similarities between the two types of alcohol. That said, it seems to me that a lot of scotches really try to play toward the oaky and peaty characters, whereas the cognacs aren't quite as obsessive about these flavor notes. Since these are the notes I like least in these kinds of drinks, I tend to like cognacs better than scotches--generally speaking, of course.