Wiliam Grant's 18-year old or Glen Grant single malt?

William Grant's 18yo is a fine blended whisky, but I believe if your old friend knows his whisky, he'd probably appreciate a bottle of single malt more than a bottle of blended.

Do you know what kind of flavor he likes? It would help a lot in choosing the right one for him, with over 90 distillery in Scotland it's not exactly simple, he might love some but hate others.

If he likes full flavored and sweet-ish whisky, consider The Macallan, The Balvenie, or Aberlour. If he wanted something light and simple, Glenfiddich fits the bill, or even Glenmorangie or Old Pulteney if he like it taste like the sea. I personally find Highland park to be a very all-rounded whisky, suitable for all moods, very sweet and bitter at the same time, very interesting, and I drink it the most compare to the others. And ofcourse last but not least, Ardbeg, Laphroaig, and Lagavulin if he likes them peaty and smoky, these are BBQ smoke in liquid form.

My personal favourite is Ardbeg Uigeadail. I get a bit emotional everytime I have a sip. It's probably one of the best out there, and probably the very reason why people like single malt over generic blended whisky.