In the first case I have to kill either one person or six but in the second I'm able to save someone and the others die, "natural" deaths or I sacrifice someone and the others live. I am unwilling to sacrifice anyone other than myself. I'm not sacrificing in the first case, I have no choice, one side or the other must die; there's nothing at all "moral" there, it's just guiding the train to do the least damage.

In the second case you have 7 people who need operations, one on the left track and six on the right. But, you have to take something from the left track to save the people from the right or, save the person on the left, no cost or transfer.