iPhone 6s (16 GB, silver, 2015)

The iPhone 6s had a 4.7-inch “3D Touch” screen at 1334×750 (326 ppi, Retina HD). The iPhone 6s cameras were vastly improved over the iPhone 6 that preceded it: a rear 12-megapixel 4K iSight camera and a front 5-megapixel FaceTime camera in 720p (the iPhone 6 used a, 8-megapixel back camera and 1.2-megapixel front camera).

The iPhone 6s was available in four colors: silver (white glass front, silver back); gold (white glass front, gold back); space gray (black glass front, medium-gray back); and rose gold (white glass front, pink-tinted gold back). 

The iPhone 6s did not use a physical Home button, but used its Taptic engine to simulate the click. It also used a Touch ID fingerprint sensor in the Home button. 

Inside, the iPhone 6s used the Apple A9 processor with 2 GB of RAM and was available in 16 GB, 32 GB, 64 GB, or 128 GB of flash storage. The iPhone 6s was the last iPhone to include a headphone jack (located on the bottom) and used  the Lightning port to connect to computer, dock, or power adapter.

This iPhone 6s example is an entry-level 16 GB model in silver with a white front. Unfortunately, this particular iPhone has a slight crack in the lower-left front screen glass (although it functions perfectly).

Source: EveryMac

iPhone 6 (64 GB, space gray, 2014)

This particular iPhone 6 model was used an AT&T network (and functioned throughout North America). All iPhone 6 models had a 4.7-inch multi-touch screen at 1334×750 (326 ppi, Retina HD display). It had two cameras: a rear 8 megapixel iSight camera (1080p) and a front 1.2 megapixel FaceTime camera (720p).

The iPhone 6 was originally available in three color options: silver (white glass front and a silver aluminum back), gold (white glass front and a gold aluminum back), and space gray (black glass front and a medium-gray aluminum back). The iPhone used a unibody design with rounded sides (similar to the iPod touch Generation 5). The glass screen curved slightly at the edges. It also included a Touch ID fingerprint sensor.

The iPhone 6 used a 1.4 GHz 64-bit Apple A8 processor with 1 GB of RAM and 16, 32, 64, or 128 GB of storage. In addition to 802.11a/b/g/n/ac Wi-Fi, Bluetooth 4.0/4.2, and LTE (4G), it included NFC for Apple Pay transactions. It had both a bottom-mounted headphone jack and a Lightning port.

Source: EveryMac.com