Danny Boy

Compare the following versions and describe the differences:
a) King Singers
b) Andy Williams
c) Declan Galbraith
d) George Benson (Solo Guitar)

Here are the opening lines:
Oh Danny Boy, the pipes, the pipes are calling
From glen to glen, and down the mountainside.
The summer's gone, and all the flowers are dying.
'Tis you, 'tis you must go and I must bide.
But come ye back when summer's in the meadow
Or when the valley's hushed and white with snow,
For I'll be here in sunshine or in shadow.
Oh Danny Boy, oh Danny Boy, I love you so.