Eu tenho 2 matrizes

Array
(
[0] => Array
    (
        [SKU] => 379
        [ProductName] => Wrap - Black
        [ProductSellingPrice] => 1.00
        [ProductQty] => 1
    )

[1] => Array
    (
        [SKU] => 3909
        [ProductName] => Wrap - Navy
        [ProductSellingPrice] => 0.00
        [ProductQty] => 1
    )

e em segundo lugar:

Array
(
[0] => Array
    (
        [SKU] => 378
        [ProductName] => Wrap - White
        [ProductSellingPrice] => 1.00
        [ProductQty] => 1
    )

[1] => Array
    (
        [SKU] => 3909
        [ProductName] => Wrap - Navy
        [ProductSellingPrice] => 0.00
        [ProductQty] => 1
    )

Eu gostaria de percorrê-los e retornar a diferença entre os valores-chave.