I think I could more easily kill a kitten than a human baby. It's the physical side, as in, it's faster and easier to kill a kitten than a human baby, say, using one's bare hands. A baby would take longer and the sounds are much harder to drown out. Much greater force is needed to do it without dragging out the process. Something as excruciating as this needs to be done in one swipe, like having blood taken.
Of course, there's the reason "A kitten is less valuable than a human being!". In the situation, I won't think that way. There's the physical, emotional side that will affect me, most. It can be best avoided by killing the kitten. It's how normal human beings think, in fact, we avoid these events because they can cause us to be guilty, question ourselves and eventually we tear ourselves to pieces. But of course it all depends. This is just me. I'm not thick-skinned enough.
I should never take on these questions, I take them too seriously.
Here's a question with considerably less moral weight. If you could make one object edible, which would it be and what would it taste like?