HTC one all the way.
Samsung doesn't have bigger camera. Megapixel doesn't mean anything, it's the camera sensor which matters. What HTC did is to increase pixel size(2 micron) , so that each pixel can catch more light, thus excellent performance in low light only comparable to Nokia 920.
What Samsung did is to decrease pixel size 1.1 micron from 1.5 micron,thus increasing the pixel count. As each pixel has much less area to catch light so they will be more noisy and consume more space as well.
This Megapixel war is just marketing gimmick, most dslr have 5,6 Megapixel. Most comp screen have 1028 pixel(full hd) display at best and even at 4 megapixel you will be downsizing your picture. I mean you won't be watching your pictures in billboard or something.
Only if you shoot in bright daylight and zoom your pictures to 100 percent then you can see more detail in s4 pictures. But HTC one absolutely kicks arse in low light performance.
Just check HTC one camera samples they are all over in net.
