The 2010 should still be maturing. The 2005 should be in its mature drinking period, so I would recommend going with it.
"The 1990s is a decade of wines now roughly 15 to 25 years old. This is the 10-year ‘time window’ during which Max Schubert said Grange would gain maturity, enabling drinkers to more easily assess its quality and potential for further development.
And, it’s true: Grange generally begins to drink at its best 15 to 25 years out from vintage.
The best Granges can last much longer – 50 years and more – but before the Grange project even began, Schubert’s stated intention was to make… ‘an Australian red wine capable of staying alive for a minimum of 20 years…’
With this is mind, the vintages of Grange likely to be at or near their very best into the 2020s are the lesser vintages of the 1990s and perhaps also the first two vintages of the 2000s – 1992, 1993, 1995, 1997, 2000 and 2001.
The aim is to catch these wines at their best. They may be good, or great drinking, but they are less likely to improve further."
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2005
Deep purple crimson. Cranberry/ rhubarb/ herb garden aromas with plenty of nutmeg/ malty seasoned new American oak. A very elemental wine with ripe cranberry/ blackberry pastille/ fruit sweet flavours, dense, grippy tannins and plenty of malty new oak characters. Finishes long and sweet. Released in 2010. Will need time to unfold. 95.9% Shiraz 4.1% Cabernet Sauvignon. Barossa Valley (including substantial proportion of Kalimna Shiraz), McLaren Vale, Coonawarra Blend. A good even vintage. Regular rainfall fell through winter into early spring establishing good soil moistures and dam levels. Mild conditions followed by a dry late summer and autumn lead to optimum fruit ripeness."