In Digital Photography ISO measures the sensitivity of the image sensor. As you increase the ISO , the sensor becomes more sensitive to light, which allows it to capture more light without slowing down the shutter speed or opening up your aperture. By choosing a higher ISO you can use a faster shutter speed to freeze the movement.
I like the first photo because the ISO is right for me and I can really see the detail on the rock and the sunlight is directed in the correct place. I personally do not like the second image because it is over-exposed and is not very appealing in my eyes. The detail of the rock isn't shown which makes it look bleached out.