Cask Strength Whisky: Pros & Cons.
Cask Strength whiskies are bottled undiluted at the whisky's natural strength. As whisky matures the proof reduces from around 70% Alc./Vol. following distillation to 50-60% after 15 years or so of maturation in barrel. This is because alcohol evaporates at a lower temperature than water. In short, natural strength equates to a more fundamental whisky experience, almost as if your tasting from casks still maturing in a distillery's dunnage house.
Given the above, the increasing popularity of cask strength single malts comes as no surprise. Such whiskies also provide an opportunity to dilute to your preferred strength rather than the bottler's. What'smore, they typically have minimal or zero filtration which tends to retain more flavour and texture.
One has to take the good with the bad. Extreme alcohol can be prickly, and can even anaesthetise the mouth resulting in a less pleasurable experience. A high tax/alcohol ratio also means such spirits can be excessively pricey.
The Holy Grail of Malt Whisky
If there was a holy grail of malt, then for many it would be the discovery of affordable cask strength whisky that's also achieved balance - to the degree that you can enjoy it undiluted. Look for examples from Glenfarcas, Glenlivet and Springbank, as well as many independent bottlings, especially those from Adelphi or Douglas Laing.