IPhone 6 vs iPhone 7 functional differences

We have observed it quite regularly that Apple does not change anything quite suddenly. Once something goes successful, they continue the trend for years together. However, there are some subtle changes that Apple has incorporated into the new devices.
Let us find the differences based on key factors-

Design
Design language remains the same across iPhone 6 and iPhone 7. There are a few smaller changes. The antenna strips from the bottom have been moved to the top. The 3.5 mm audio jack is gone. It has been replaced by the Lightning port.
IP67 waterproofing has been introduced. There is a Home button redesign. There are new colors introduced.

Display
The Display remains same. The size of the screen stays the same at 4.7 inches with the same resolution at 1334 x 750 pixels and 326 ppi pixel density. Apple has claimed that the display on iPhone 7 is 25 percent brighter. We do not how as Apple has not come clear on it.

Camera
The rear camera on both iPhone 6s and iPhone 7 read 12 MP. All the other features remain the same. The iPhone 6, however, had a 8 MP camera. From that point of view, we can assume that the camera has been upped on iPhone 7.
The front camera has received a boost. The camera has been upped from 5 MP to 7 MP. Optical image stabilization has been introduced on iPhone 7. The iPhones before this year never had OIS.

Hardware
iPhone 7 comes with new processor - A10 fusion chip. It is said to be 40 faster than the A9 processor and two times faster than A8. Also a new improved GPU has been added though Apple has not revealed exactly which one.
There has been an improvement in the battery performance as well. It is supposed to be two hours longer than previous models. There has been a change in the storage capacity as well. The 16 GB model has been scrapped.

There are these following differences that one can make out between the two iPhone models, iPhone 6 and 7:

Size and Design
Apple has incorporated a 3.5mm Lightning connector in the iPhone 7 box and apart from this there is no such major difference in the size except in their weight.

The size and dimension of iPhone 7 is 138.3 x 67.1 x 7.1 mm weighing 138 g (4.87 oz)
The size and dimension of iPhone 6S is 138.3 x 67.1 x 7.1 mm weighing 143 g (5.04 oz)

Where the iPhone 7 has enhanced in its solidness with a Series 7000 aluminum from the iPhone 6S model which has a IP67 tidy and water resistant body that allows the telephone to survive even when completely submerged in the water for up to 30 minutes.

Minor Changes in Display
There are some minor changes in the display between both the phones and here they go:

The iPhone 7 display is of 4.7-inch having a LED-backlit IPS LCD, with 1334 x 750 pixels (326 ppi) having 65.6% screen-to-body ratio
The iPhone 6 display is of 4.7-inch having a LED-backlit IPS LCD, with 1334 x 750 pixels (326 ppi) having 65.6% screen-to-body ratio

Apple has boosted up the peak brightness on their iPhone 7 by 25%, by introducing a wider (P3) colour gamut and with better support for colour management along with a "cinema standard" display.

Performance Wise
The iPhone 7 has in it the Apple A10 Fusion chipset with a Quad Core CPU, a Six Core GPU, and RAM of 2GB
whereas the iPhone 6S is having an Apple A9 chipset, with the Dual-core 1.84 GHz Twister CPU, a PowerVR GT7600 GPU with 2GB of RAM.

The Camera
The iPhone 7 is sporting a 12 megapixel sensor sensor camera in the Rear that has f/1.8 aperture, with Focus Pixels and Optical Image Stabilisation It is also having a quad-LED (dual tone) flash with 4K video recording feature. The Front Camera is of 7MP sensor with f/2.2 aperture and 1080p recording.
On the other hand the iPhone 6S has the same 12 megapixel sensor in its Rear with f2.2 aperture along with Focus Pixels, and Software Image Stabilisation. It too has dual-LED flash and the capability of 4K video recording. The Front Camera is of 5MP with f2.2 aperture and 720p video recording.

Iphone models have improved over the years with the features. However this year the feature set has also done some of the drastic improvement in the design and functionalities.

Removal of Design Features Iphone 7 series has undergone removal of features. You can't use the headphone jack anymore. There is also removal of antenna bands. These two features were present for earlier iPhone series. In case of Iphone 6s & 6 you may not find any such feature.

Home Button Service Feature Some of the iphone 7 tests have shown that apple is more responsive towards the defects found in the device. Home button if becomes malfunctioned will create a popup message asking you to visit the service center. This feature may extend to other parts of the device in upcoming iOS update. In case of Iphone 6s and 6 there is no such service messaging.

Battery LifeIphone 6 and Iphone 7 has a big battery improvement jump in between the models. The iphone 7 is known to have 2 extra hours of battery.

Processor Iphone 7 has the A10 Fusion processor along with the M10 motion co-processor. In case of Iphone 6S it had the A9 processor which lags 40% than the current A10 processor. Iphone 6 being A8 processor product obviously lags a bit in the area of performance than the A10.

Camera Iphone 7 has 12-megapixel sensor with f/1.8 aperture and six-element lens. In case of Iphone 6s and 6, both the models have both had similar 12 megapixel spec but change in aperture with f/2.2 lens. All three set of compared phones have the capacity for 4K recording, body detection, face detection and front flash. So in terms of spec there isn't much gain when it comes to camera. Only difference being 1080p images from Iphone 7 seems to have sharper picture than the earlier models.

Display Iphone 7 and Iphone 6s and 6 seems to have pretty much same display configuration. All the compared devices have the same screen size of 4.7''. This LED display in all the devices have 1334 x 750 pixels (326 ppi). The only difference being the Iphone 7 having P3 colour gamut. Also Iphone 7 and Iphone 6s has the 3D Touch which is missing feature in Iphone 6.

iOS Software The iOS 10 update inside the iphone 7 has made device specific improvements. In case of the iphone 6S and 6, the last few months the iOS 10 update has been released. So there is nothing drastic improvement on this side if we compare these three models.

Though some of the updates in between the phone are just cosmetic. If you're casual user you may not notice much changes unless you're using specific feature like audio jack or if you use the phone for taking images regularly.

There are some of the best comparative features between Apple iPhone 7 and Apple iPhone 6 listed below:

Design
Both the Apple iPhone 7 and iPhone 6 have similar physical design but only few changes have been made. The iPhone 7 has IP67 waterproof technology, and iPhone 6 has normal waterproofing technology. The iPhone 7 has Black and Jet Black color also with Silver, Gold and Rose Gold and iPhone 6 has Space Grey, Silver and Gold colors. The iPhone 7 has redesigned their home button which iPhone 6 remains same in its home button features. In iPhone 7, the lightning port and stereo speakers were added as another advantage. The dimension of iPhone 7 has 138.3 x 67.1 x 7.1mm and iPhone 6 has 138.1 x 67 x 6.9mm. The total weight of the model iPhone 7 has 138g and iPhone 6 has 129g.

Display
Both the iPhone 7 and iPhone 6 have 4.7 inch size. The iPhone 7 comes with retina HD display while iPhone 6 has LED backlight display. Both the iPhone 7 and iPhone 6 have 1334 x 750 pixels with densities of 326ppi. The iPhone 7 features 3D touch while iPhone 6 does not have this feature.

Cameras
The iPhone 7 comes with 12MP rear camera and 7MP front facing camera. It has the aperture of f/1.8 and a new six element lens. The iPhone 6 has 8MP rear camera and 1.2MP front facing camera. It has the aperture of f/2.2. The iPhone 7 has optical image stabilization with Quad LED true tone flash. It also brings body detection sensor and wide color capture. The iPhone 6 also has optical image stabilization with Dual LED true tone flash. The iPhone 7 has retina flash will record 1080p in front facing camera while the rear camera captures 4000p. The iPhone 6 doesn't have front flash technology but it is capable of recording videos.

Hardware & Software
The iPhone 7 has A10 fusion which is the newest version of processor. It has M10 motion coprocessor which is faster than the A9 and A8 versions. The iPhone 6 has A8 version processor with M8 motion coprocessor. The iPhone 7 has 2GB of RAM memory where iPhone 6 has only 1GB of RAM memory. The iPhone 7 has 32GB, 128GB and 256GB of storage space where iPhone 6 has 16GB and 64GB of storage space. The battery life of iPhone 7 model has 16 hours when iPhone 6 has only 14 hours. The Apple iPhone 7 runs in iOS 10 which is the latest version of Apple. The iPhone 6 model runs in iOS 8 and also upgradable to iOS 10.1 version.