The underpainting one looks more vibrant. I dont know how to say but it almost looks that zhe shadows on the underpainting one are softer. Thank you for sharing
One thing you might want to consider is how the order of the paintings factor into it. You have gain much experience developing the skin tones for values and color accuracy from the first painting making the second painting easier. You may want to try to experiment again doing the under painting painting first and see if you arrive at the same outcome.