21yo is good, although I could sense some differencies with 25yo but I can't describe exactly what is the difference. Nose is excellent in both and in both it promises a lot more to taste than can be found. Taste is easy, very enjoyable, somewhat complex but surprisingly short. I feel that 25yo might be bit sweeter/more sherry in taste and I think it's bit better, but this sounds ridiculous when thinking about 21 years and 25 years.
I must try the younger ones someday ...