All in all as expected two very comparable drams with a slight advantage to the 59, as this is more balanced and rounded. By the way, a very interesting experience to do such a cask pairing...
PS: I paid just 57 Euro for bottle no. 229 of cask 3958 in July 2006 and just 68 Euro for bottle no. 079 of cask 3959 in February 2005.
At the first impression there is not much difference, maybe the 59 is a little bit sweeter while in the 58 there are slightly more wooden notes. But both have a quite pleasant and complex nose mostly on floral aromas and both open up nicely on water added, again with a slight advantage for the 59 as being rounder and more balanced.
The 58 now has significantly more bitter wooden notes than the 59, which is more rounded in that respect. With water the woodiness of the 58 is gone while the 59 stays pretty much the same as if neat. Again, the consistency and balance of the 59 is better than with the 58, but both are very fine drams, for sure. The slightly bitter notes of the 58 decrease over time, leaving space for the same nice sweetness and balance as with the 59. Water clearly improves the mouthfeel and taste of both with the 58 winning more than the 59.
Both own a medium long finish which is a little bit drying, but not unpleasantly. The sweetness coats your tongue and mouth even minutes after swallowing, in this respect the finish is quite long. It shortens with water, so while I like the nose and taste better with water added, I find the finish more appealing when neat.