Witch speedlight is better and why?

I would like to get a speedlight. I like to do nature photography and I do not need something that great.
Witch is better and why.

The Yongnuo YN-468 II or the Yongnuo YN-560 II

You can give me some technical reasons. I'm fairly good with camera knowledge.
The Yn-468 II it an i-TTL flash. I shoot with a Nikon D3100.
the Yn-468 II has a trigger voltage of 3.3 volts. Is that right?
I like to work with available light and do not need the best in the west.

No matter what external flash you buy, you need to make sure that it is iTTL compatible with your camera.

If you are working with availaible light, then there's no need for a flash. This part of your question makes no sense. In addition when shooting animals, using a flash will only give you one shot since it will most probably spook the animal.

There are two main differences. Guide number is 33 meters for the 468, and 56 for the 560 model. That means the 560 is a full stop more powerful than the 468. Also, the 560 has a wider zoom range for the flash head, extending from 24-105mm.

For what you want to do (and almost any other flash work) the more powerful flash is always the better choice. Since the 560 is a stop more powerful for about the same cost… The answer should be pretty simple.