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Trying to compare Jack Daniel's and any Johnnie Walker blended Scotch is like comparing apples and oranges - two entirely different beasts. Also, I've never heard of Johnnie Walker White Label. Perhaps you're referring to the new 18-year old Platinum Label? If so, I haven't had the opportunity to try that one as yet.
In the Jack Daniel's stable, I'd describe some of the offerings as follows:
The regular Old No.7 - fairly unchallenging and a tad rough around the edges. Better as a mixer than as a sipper.
Gentleman Jack - Much, much smoother, and one you can actually sip and enjoy. Overall, however, not an exceptional pour by any stretch of the imagination.
1954 Gold Medal - A lot more character, with the spices bouncing around the palate. Clean distillate with no off notes.
Single Barrel - The combination of higher alcohol and greater maturity brings added textural richness and length of flavour. More expensive, to be sure. But if you're set on a JD, this is the one I'd recommend.
Now to Johnnie Walker Blue Label. In the final analysis, this one's a status symbol, and unfortunately little more (especially given the care that is supposedly lavished on its production). Nice whisky? Absolutely. Worth the asking price? Nope. Why? Because for the same price (or less), you could purchase any number of superior blended Scotches, blended malt Scotches or single malt Scotches. Don't forget that the Johnnie Walker lineup of blended Scotches is aimed primarily at the widest possible drinking audience worldwide. It is, therefore, something of a cash-cow for Diageo.
Hooked on the idea of buying a Johnnie Walker whisky? Search out any remaining bottles of the Gold Label 18 Year Old (a blended Scotch presently being replaced by a no-age-statement Gold Reserve and the way too costly Platinum Label 18 Year Old) or the Green Label 15 Year Old (a truly excellent blended all-malt Scotch) before they disappear from the shelves.