Back to the PHP manual page i linked to about logical operators:
$a || $b Or TRUE if either $a or $b is TRUE.
$a && $b And TRUE if both $a and $b are TRUE.
So think of it this way:
If you want the content to show if any one of the conditions is true, use OR.
If you want the content to be show if all of the conditions are true, use AND.
So to look at why and works for you're condition with $row_rsPROD['LEDid'] equal to 610
$row_rsPROD['LEDtypeID'] != 6 False
$row_rsPROD['LEDtypeID'] != 9 False
$row_rsPROD['LEDid'] != 610 True
only one condition is true so the if fails and the content is hidden