If we vary the example, I think we can bring out a difference between the two forms.

Bali is one of the Indonesian islands which is visited by many tourists.

Bali is one of the Indonesian islands which are visited by many tourists.

It seems to me that in the first sentence we are given two pieces of information about Bali. It is an Indonesian island and it is visited by many tourists. In the second sentence, however, we are told that Bali is one of the Indonesian islands and that those Indonesian islands are visited by many tourists.

Bingley

Bingley