As a professional violinist, it is difficult to explain why playing instruments by these two makers is so wonderful. I would imagine part of the wonder is the way they suggest a way of coaxing the best out of you.
The Stradivari dates from 1696 and the Guarneri from 1704, truly remarkable in construction, they are stunning both visually and from an aural standpoint utterly beguiling. Married to a first class French bow, the player is set free to a remarkable degree.