Okay it's time for me to give you my thoughts on my Shootout. I found the iPhone shot videos about 2 notches on the cool side and was pretty much bland. Much like the Canon DSLR neutral preset setting. Where the iPhone excelled at was focusing. For the Lumia, it was about 3 notches on the warmer side and was much more sharper and saturated. More like the Landscape preset on the Canon DSLR. So it's pretty much subjective on what the person likes. I tend to like the bland settings because I like doing Post Processing and add sharpening in Premiere. Where the Lumia excelled at was Macro and manual controls. You can really get close to the subject to focus, I'm guessing about 3" minimum focus distance. Where the iPhone was about 6". I do wish the Lumia had more manual controls such as locked exposure and ISO, so you wouldn't see the fluctuations. Kelvin White Balance controls would be nice too in addition to the WB presets. I also did experience some camera app crashes on the Lumia, maybe it's my SD card but my SD card is a Sandisk U3 rated at 95mbps. When I switched to record on the Phone Storage (I had to choose pictures in storage settings, setting for videos didn't work) I didn't experience the crashing. Both phones dropped frames when recording 4k at the beginning of the recording.
Which ever phone you get, they're both great at recording video. The iPhone will pretty much get you a decent video every time but there's much more potential with the Lumia using manual controls. Also Lumia's have been known to get updates to improve camera and video quality/capabilities where the iPhone's don't get the added features unless you upgrade to the latest model.
For me the iPhone won the first shootout and the Lumia won the second. But I honestly really cannot tell much off a difference in quality between 1080p vs 4K on these phones (Yes I have a 4K monitor). To me the less storage space and less horsepower needed to edit a 1080p video outweighs the benefits of the increased resolution of 4K. Plus you need a 4K monitor or TV to enjoy it.