Let's start here: if you're a dyed-in-the-wool scotch drinker and you haven't at least branched out into trying a mezcal or two, there's no time like the present to expand your horizons.
At least from my inane, non-professional frame of reference, tequila has a lot in comparison to cognac. Both are delicious, but they're fairly tightly controlled by production region, acceptable finishing processes, final ABV, aging critereon, and distillate base. This is a double-edged sword. On one hand, you know the level of quality you can expect and a general flavor profile, but the range of possible tastes is narrowed.
In this sense, mezcal is truly the spirit for mavericks. It comes from distilleries in towns that look like they could have been featured in the movie Desperado. The spirit comes from stills that look like they would be right at home in a Mad Max film. At times, the distillers choose to throw in chunks of raw meat for flavor. I swear to god, it's the wild west out there.
Mezcal begins with the choice of the distillate base. The most common variety of agave used is espadín (as opposed to the Blue Weber agave used for all tequilas). However, various exotic varieties like tobalá and arroqueño can be sourced. Some varieties are known for being fruity, rich, savory, or chocolaty. Sometimes they find whatever's growing on the side of the mountain and mix them all together. Be warned: the exotic varieties are expensive. (More on this later.)
Once they settle on the variety to be used, they literally kick the agave hearts (piñas) into a smoldering pit and cover them over with earth. Traditional methods of mezcal production then involve using a massive wheel called a tahona to crush the cooked hearts of the agave plants. Usually this wheel is burro-powered, just in case you felt like the production methods of mezcal could stand to look a little more like something out of Mel Gibson's Apocalypto. Typically mezcal is distilled and bottled without any degree of barrel aging.
But here's the deal: this lunatic combination of primitivism and pragmatism results in an extremely bold, earthy spirit with a huge range of flavors. I really believe that mezcal is a kissing cousin to scotch in the way that two bottles can differ from one another. Hand me a reposado tequila from a quality producer, and I basically know what I should expect in terms of taste. Hand me a bottle of mezcal and it's a mystery until I dig in. For the adventurous, that's a selling point.
If there's a knock against mezcal, it's that the real exotic production methods and unusual varieties of agave tend to carry a huge markup. We're talking in the neighborhood of $90 - $120 a bottle, which is often enough to get you a tremendous bottle of scotch from a well-known manufacturer. Maybe that's an apples-to-oranges comparison, but even for a guy like me that kind of spend is a difficult proposition for unaged spirit. Especially when the variance from bottle to bottle means I don't really know where something comes from.
That said, there are a lot of truly delicious mezcals that are indeed affordable. Our mezcal category will show you a lot of the ones I tend to like, but off the top of my head these would all make for solid recommendations:
Fidencio Sin Humo - Literally translated to "no smoke," I think this is a good introduction to the boldness and richness of mezcal without the ashiness that can be off-putting to some. A good balance of sweet and savory in this one.
Alipus San Andrés / Santa Ana Del Rio - Better known as "pink" and "green," respectively. The pink has a lovely, creamy citrus sweetness to it. The green is brooding and earthy. Both are stellar options in a great range of mezcals.
Del Maguey Iberico - At $200 a bottle, this stuff is seriously good. Apparently when you dangle a leg of Iberico ham in your vat of mezcal, magical things happen. I haven't yet sprung for a bottle of this, but a friend and I tried this in a mezcal bar more than a year ago and we still haven't been able to get it out of our heads.