DeanSheen noted that some people may prefer the 12yo to the 18yo, so I pulled a bottle of each for direct comparison.
Color of both were nearly identical. Nose for both were similar with the 18yo being a little heavier. Both had very little wood flavor which is surprising given the age. Both had a similar light aftertaste.
The 12yo seemed similar to a Speyside with more spice and leather. The 12yo had an unusual, very subtle, lingering aftertaste that was NOT unpleasent but is reminiscent of tobacco smoke aftertaste..
The 18yo is a different animal entirely. More spice, leather, and an abundance of flavors. One flavor hits the tip of tongue hard, another hits the side/back, and another hits the very back - a veritable explosion of different, unusual flavors. The 18yo has considerable complexity and depth with unique flavors not found in other whiskeys I've sampled. Though the initial aftertaste is mellow, there is a long. lingering, subtle, perfumey, aftertaste.
I understand why some would prefer the 12yo; it has a more traditional profile similar to other beverages on the market, yet offers its own character. And the 12yo is more affordable at about a third the cost of the 18yo. However, I like unusual flavors and the 18yo provides that and more. In a blind taste test with 200 samples to choose from, I'd be hard pressed to tell most drinks from another, but I could definitely pick out the Yamazaki 18yo. This is one fantastic drink and every whiskey afficienado should sample it at least once.