Now that the iPhone 6s Plus can record 4K videos, it is finally on par with the competitions. So, it's easier to compare the available modes.
Apple iPhone 6s Plus captures 4K @ 30fps, 1080p @ 60fps, 1080p @ 30fps, 720p @30 fps. The available slow-mo options are 1080p @120 fps and 720p @240fps.
Samsung Galaxy S6 edge+ captures 4K @ 30fps, Quad HD @ 30fps, 1080p @ 60fps, 1080p @ 30fps, 720p @ 30fps and VGA @ 30fps. The available slow-mo option is only 720p @ 120fps.
While both phones seem like quite capable camcorders, the iPhone captures only mono sound in videos at 81Kbps bitrate. The Galaxy S6 edge+ videos on the other hand have 256Kbps/48kHz stereo audio.
Really, Apple, is that hard? Since the iPhone 6s Plus, the most powerful smartphone on the market, comes with two microphones, we can't fathom why Apple isn't enabling the stereo sound. We guess it needs to be reinvented in a proper way, hopefully in a year or two. Or ten.
Apple's 4K videos carry a bitrate of around 51Mbps, the 1080p videos at 30 fps have a bitrate of 17.6 Mbps, keeping the same audio, while the 60fps ones came out with 26Mbps bitrate.
Samsung's 2160p videos are shot at the usual 48Mpbs total bitrate, the 1080p videos at 30 fps have a bitrate of 17.1 Mbps, keeping the same audio, while the 60fps ones came out with 28Mbps bitrate.
The 4K videos shot with the iPhone are slightly less processed than its still images - there is some noise, but less over-sharpening while the detail is decent if not quite class leading. Dynamic range is once again impressive and the frame rate is pretty steady, but the mono audio is disappointing.
The Galaxy S6 edge+ 4K videos also offer great dynamic range, though notch lesser than the iPhone's. They offer more detail, less noise and better sharpness though. The colors on the iPhone are warmer, while the Galaxy's are more accurate and close to reality.
Here is a crop from 4K videos shot side by side. Note that the Galaxy video is a bit overexposed, but this isn't a common issue.
And you can click the picture below for the full resolution crops.
The same findings apply for the 1080p videos - decent amount of detail, high dynamic range and superb contrast. While both phones do great on the 1080p capturing as stand alones, a side by side comparison reveals the Galaxy S6 edge+ videos have more detail and are much sharper.
Winner: Samsung Galaxy S6 edge+. The 4K videos offer more detail and stereo sound, which is enough for the win. The iPhone 6s Plus also offers great videos, but the mono audio is crippling them.
Both cameras boast Optical Image Stabilization, but Apple has decided to keep its digital stabilization active. It's one of the best around, but it narrows the FoV and shouldn't be needed on an OIS camera.
The OIS/digital stabilization combo seems to have worked for the iPhone 6s Plus, it absorbs the shake of footsteps better and its video appears to float smoothly. The Galaxy S6 edge+ corrects small shakes okay, but there's jerkiness left uncorrected.
Winner: Apple iPhone 6s Plus. The always-on digital stabilization eats into the FoV, but handheld videos are pleasantly smooth.