Pretty much what robbo said, although could be something out in the next month or two regarding motorola's phones.....
Main advantages of the GS 4 camera are;
- if you crop/zoom in on images, have a very high res. display and/or print photos on large paper.
- Bright landscape conditions
- panorama shots
-features/options overall
Main advantages of the one camera:
- very fast shutter and combined with OIS, you get more consistent/usable photos, more so in lower light conditions and/or with movement shots
- indoor conditions, low light/dark conditions
- much larger FOV
- audio recording (really amazing in loud environments) and video recording overall (GS 4 looks excellent for 1080P recording but the OIS, FOV [which is further reduced on the gs4 when you enable image stabilisation] etc. give the one the edge by quite a bit imo)
The GS 4 can perform superbly in low light/night conditions with "night" mode but it comes at a cost, slower shutter thus only useful with non moving objects and you need to have a steady hand.
Regarding the features/options, both seem to be more or less the same, GS 4 has the edge with a few more things to choose from. Most of the one's features are tied to the zoe feature and gallery i.e. sequence/drama shot, always smiling, eraser/removing objects etc. where as the features on the GS 4 are selectable through the camera app.
Macro shots look superb on both, need to see more from the GS 4, personally I prefer the one macro shots as they just have a very "natural" look to them but the difference isn't big enough to be worth worrying about.
Up to you this part, but photo size is quite different due to the difference in MP, talking about 1.5MP on average for the one VS 6.5MB for a photo from the GS 4
EDIT:
Both cameras will improve with updates, the one is getting an update currently that has brought a nice improvement overall.
