Do the iPhone 7 and 7 plus cameras use the same sensor? I am looking to upgrade to the latest iPhone mainly for the camera.  I am wondering if the iPhone 7 and 7 plus use the same camera sensor.  Specifically, will they handle the same in low light conditions.  I shoot a lot of low light photos and am curious if they will perform the same.
SHORT ANSWER

If it was me and my main interest was in photography, I'd definitely opt for the iPhone 7 Plus over the iPhone 7. Don't get me wrong, both the iPhone 7 and iPhone 7 Plus have great camera systems, but the iPhone 7 Plus has a few features over the iPhone 7 because of its secondary 56mm-equivalent "telephoto" lens system. And, since you're main interest is in low light conditions, you should be aware that Apple markets the iPhone 7 Plus as being the one to use for low-light photography.

LONG ANSWER

Let's start with the specs - below is a summary of the camera specs of each:

iPhone 7 Plus


PRIMARY CAMERA: Dual 12 MP (28mm, f/1.8, OIS and 56mm, f/2.8), phase detection autofocus, 2x optical zoom, quad-LED (dual tone) flash. This features: 1/3" sensor size @ 28mm, 1/3.6" sensor size @ 56mm, geo-tagging, simultaneous 4K video and 8MP image recording, touch focus, face/smile detection, and HDR (photo/panorama). Video recording at:   2160p@30fps, 1080p@30/60/120fps, and 720p@240fps.
SECONDARY CAMERA: 7 MP (32mm, f/2.2), face detection, HDR, and panorama. Video recording at: 1080p@30fps and 720p@240fps.


iPhone 7


PRIMARY CAMERA: 12 MP (28mm, f/1.8, OIS), phase detection autofocus, and quad-LED (dual tone) flash. This features: 1/3" sensor size, geo-tagging, simultaneous 4K video and 8MP image recording, touch focus, face/smile detection, and HDR (photo/panorama). Video recording at: 2160p@30fps, 1080p@30/60/120fps, and 720p@240fps.
SECONDARY CAMERA: 7 MP (32mm, f/2.2), face detection, HDR, and panorama. Video recording at: 1080p@30fps and 720p@240fps.


As I mentioned earlier, Apple pushes the fact that the iPhone 7 Plus is ideally suited to low-light conditions. They even produced a video to highlight this. It's called Midnight and you'll see that the iPhone being used is an iPhone 7 Plus (this is obvious when the user picks his iPhone up at about 5 seconds in).

In summary, with an iPhone 7 Plus you can use the 28mm-equivalent wide-angle lens using Photo mode, zoom up to 10x (digitally), and take snaps with an added depth of field effect using Portrait mode.

If you do a Google search I'm sure you'll find lots of info about the advantages of an iPhone 7 Plus camera system compared to the iPhone 7. I'm sure if you read some reviews you'll find some that tested each in low-light conditions for you to compare.