There are a lot of similarities between the 7D Mark II and the 80D. Here's a rundown of the most significant differences:

• The 80D has slightly higher resolution, but it's not that significant. 6000 pixels wide vs. 5472 pixels is less than a 10% difference.
• The 7D2 has two DiG!C 6 processors, the 80D has one. This enables the 7D2 to use iTR that incorporates info from the RGB+IR light meter with predictive Servo AF tracking. This is a distinct advantage when shooting sports and action.
• 7D2 has a 150,000 pixel RGB+IR light meter divided into 252 zones vs. 7,560 pixel RGB+IR meter with 63 zones for the 80D. The 7D2 will probably "guess" better when metering in very difficult lighting conditions, but both are very, very good in this respect.
• 80D has both ambience and white priority AWB, the 7D has only white priority WB. This only has any real effect if saving straight to jpeg since the WB can be totally changed in post with no loss of image quality with raw files.
• 7D2 has a slightly larger viewfinder. Both cameras show 100% of the frame, but the 7D2 is magnified at 1.00x vs. 0.95x for the 80D.
• The 7D2 has user changeable focusing screens. Canon currently offers the Super Precision Matte screen in addition to the standard focusing screen. Third party makers may also offer other focusing screens for the 7D2 since it is user removable. The 80D's standard focusing screen is not user removable. If you plan on using manual focusing via the viewfinder, this gives the 7D2 an edge.
• 80D has a Vari Angle touch screen, the 7D2 has a fixed screen. Both are the same size and resolution. If you like using a movable screen the 80D is the clear winner here.
• The 80D has a slightly stronger built-in flash (GN12 vs. GN11), the 7D's built in flash can do Multi flash (several distinct pulses during a single shutter opening). Neither is very powerful compared to external flash options.
• 80D has several 'Scene' exposure modes (Portrait, Landscape, Close-up, Sports, Night Portrait, Handheld Night Scene, HDR Backlight Control, Food, Kids, Candlelight) and creative filters (Grainy B/W, Soft focus, Fish-eye effect, Art bold effect, Water painting effect, Toy camera effect,Miniature effect) but only one programmable 'Custom' mode. The 7D2 lacks the creative filters (which can be done better in post-processing with either camera) and 'Scene' modes but allows the user to save three 'Custom' modes.
• The 7D2 includes in-camera HDR with 5 presets.
• The 7D2 can shoot at 10fps for 31 raw image files or until the memory card is full when shooting jpegs with the fastest UDMA-7 CF cards. The 80D can shoot at 7fps for 25 raw or 110 jpeg images with the fastest UHS-1 SD cards. There's not much that is more frustrating when shooting sports/action than seeing a "money" shot in the viewfinder while waiting for the buffer to clear. The 7D2 has an edge here.
• The 80D has user selectable adjustments for AF tracking in Live View Movie mode. The 7D2 has more user selectable options in PDAF mode shooting still images. In terms of AF, the 80D is a slightly better video camera, the 7D2 is a better sports/action camera.
• The 7D2 has built-in GPS but requires the $40-50 WE-1 card in the SD card slot for WiFi. The 80D has built-in WiFi and NFC but lacks built-in GPS.
• The 7D2 has a USB 3 interface, the 80D is USB 2.
• The 7D2 has one CF and one SD card slot that can be used to either mirror all images, store all images in different forms on each card (i.e. raw on the CF card and jpeg on the SD card), or store different images on each card (i.e. fill one, then fill the other). The 80D has a single SD slot. For redundancy and data security the 7D2 is the clear leader.
• The 80D is rated at about 40% more still images from the same LP-E6N battery as the 7D Mark II. Extra batteries are pretty cheap, especially high quality third party ones that can outperform the OEM batteries, but the 80D is the clear leader in this category.
• The 7D2 has a magnesium alloy body, the 80D has a polycarbonate resin/glass fiber body. The 7D2 is built a bit tougher and can handle worse environmental conditions than the 80D.
• The shutter durability rating for the 7D2 is 200,000 actuations vs. the 80D's 100,000 actuation rating. The 7D2's shutter should, on average, last twice as long.
• The 7D2 is about 6.5 ounces heavier and slightly larger than the 80D.

In the end it basically comes down to which you would enjoy the benefit of more: More options when shooting video, a Vari angle touch screen, and 'Scene' modes when you're not sure how to set exposure yourself for a specific scenario from the 80D versus more shooting speed, better Servo AF tracking, and more user configurable custom modes with the 7D Mark II.

The 7D Mark II can take a little more punishment and should last a little longer under the same usage patterns than the 80D.

The 80D has a sensor that is two years newer technology and does slightly better in terms of dynamic range and signal-to-noise ratio at low ISO settings. At higher ISOs the 7D Mark II takes the lead in SNR and DR. This means the 80D might be a slightly better portrait camera in a controlled environment with studio lighting, especially when using low key styles of lighting (Both would be bested in this respect by a FF camera, such as the 6D Mark II). The 7D Mark II is better at shooting events and sports in existing low light.

Most of the 'creative filters' of the 80D can be done better with raw image files in post-processing. That same capability would also naturally apply to raw files from the 7D Mark II.

I would rarely if ever use the 'Scene' modes if any of my cameras (I primarily use a 5D Mark III and a 7D Mark II as well as a 5D Mark II) even had them. On the other hand, I often set up my cameras in advance with 2-3 'Custom' modes that allow me to switch between them almost instantly instead of having to change a large number of settings individually. This is especially helpful if you are shooting in an environment where you need to switch back and forth between two different approaches. For example, an outdoor event where some of the action is away from the sun and some is towards the sun, or a night athletic event where the field is much better lit than the stands but you need both action shots and crowd reaction shots (the best of which tend to happen immediately after the best action).