"- is it safe to buy class A amp of that age ? "It depends on how it's been treated previously... if played regularly but not left on all the time & placed in a cool environment, go for it!
- which of the two would be the better choice ?That's very personal; I would go for the class A, but I find Esoteric a tad on the dry side. Both amps are very well engineered IMO.
Generally speaking, however, I find both your options very expensive!
There is no shortage of outstanding used components available well below 7.5-8k euro... and new stuff at that price as well (musical fidelity nuvista 800 comes to mind...).