Poor performance of HDR in Nexus 5

I am using Nexus 5, and the image taken with HDR is very poor quality. I have updated to 4.4.2, still no improvement. So to make sure I am doing it correctly, I installed another app "Best HDR" and compared images with that of Android and the first one is much better. I will put the two images here (images are compressed for fast uploading, so they will be a little blurry than the real): Taken with Android HDR / Taken with Best HDR (click images for larger variants) --- Taken with a normal camera (click images for larger variants) Taken with Android HDR / Taken with Best HDR (click images for larger variants) **Question**: Why is it like this? Is the HDR of Android that bad or am I doing anything wrong?