[Xperia Z3 General] juanmaasecas:
Downsized shots:

First shot.

It's about exposure. I think A picture is a little bit overexposed. Contrast and colour in the steak are off. B picture is way more pleasant. The detail level at those resolutions is quite similar... B picture WB is a warmer and probably it's more accurate in A, but I still prefer how it looks in B...

Second shot.

Same story than the previous picture. In this case, A is warmer and B is overexposed. I like A the best since it seems more natural

Keyboard shot.

A picture is a lot brighter, but very unnatural. The grain size is huge, horrible. Noise reduction has taken off every fine detail and it's very overprocessed. B picture is darker but more pleasant to my eyes, even I think it preserves more details...

Cat shot.

Look at the cat's ear in A, or at the floor... The picture looks very plain. Lots of texture loss everywhere, plain colours, etc. It seems like when you use a "beauty" effect to remove the blemish in your face, but with the cat. B picture seems better, altough it's probably because there's better light and better contrast...

Looking at the full-res pictures.

First shot

It's incredible how at 100% zoom Xperia picture shows better detail, even at double ISO level (250 Xperia, 125 iPhone). I'm not fully convinced about Sony processing here, but neither about Apple's. It seems like a watercolor...

Second shot

Same story. Watching at 100% zoom, Xperia shot shows more artifacts, but iPhone shot shows an agressive noise reduction.

Keyboard shot.

No surprises here. I liked how Xperia was better at higher ISO level than iPhone, but at this level (12.800 ISO) Xperia picture is awful. I agree there are a lot of advantages in having such capability, but the detail is very low, the picture is too overprocessed, etc.

Cat shot.

Surprise! You tricked us here! The difference is in lightning as I guessed. Using ISO 800 (a little darker scee), Xperia processing is worse... At 320 ISO it's still OK, altough watching the picture at 100% zoom, I'm not convinced either.

Conclusion: iPhone 6 plus processing is a step back respect 5/5s IN MY OPINION. More noise reduction means less detail and less natural picture. There are plenty of threads discussing about how bad the new iPhones do with the processing at macrumours.com (for example).

Xperia Z3 is very good at not-too-high ISO levels and in macro. The processing is not the best, the pictures shows a lot of artifacts, and texture and fine details are lost (because of that, macro pictures looks very good, but when looking at a landscape, folliage, etc, it usually sucks...).

Conclusion 2: At "normal" picture sizes, if we're not doing pixel peeping or zooming too much, both iPhone and Xperia are very similar (and almost every cameraphone nowadays) in a lot of scenes, and sometimes the differences are only on exposition and WB and I'm glad to see you can shoot faster and using a higher ISO level with the Xperia and still be quite good (if not better overall...)

Pd: Altough I'm still using an iPhone 5s right now and I'm very happy, I miss Sony and android sometimes and probably I'll own another Xperia in the future, but I wish I could choose RAW format file... I want natural images! Give me the noise! Let me reduce the noise by my own at the level I prefer!