The HP 25 is unbelievably yummy! I adore it. The Balvenie 21yr is also incredible. I would die happy if those were the only two whiskies that I could drink for the rest of my life...
I haven't had the Tun.
Glenfarclas makes a great whisky. I love their 15yr, the 17yr is nearly as good, and the 25yr is fantastic. The 21yr was good, but not as good as either the 25 or 15/17. In fact, the 15yr might be the best of all of them (stronger flavor profile).
I haven't had anything by Macallan older than the 18yr. I don't like the 18yr enough to justify its price, so spending even more money on the 21/25 is just not going to happen.