Default seems nice to me. I used a few but there is not much difference in the quality of the pictures and as far as design and usability goes the default is one of my favorites. If there were RAW format shooting I would use another app for sure but for shooting jpegs defualt is great.
It has lot of parameters, (U can adjust the brightness, sharpness, contrast...) and it has mutch better jpg-motor, than the stock app. And if you want a little bit better framerate, in low light conditions try the Open camera app, and set the ISO to 100 manually , it makes the video a little bit darker, but the framerate is better than any other apps.