If you are shooting soccer, especially at night under stadium lights, the 7D Mark II is a far superior camera than the 70D for that purpose.
The four areas where the 7D Mark II outclasses the 70D for that use case are Autofocus performance (in terms of speed, consistency, and overall accuracy), more accurate exposure control with a color sensitive light meter, handling speed, and the flicker reduction feature Canon has included in several cameras since it was first introduced in the 7D Mark II a little over a year and a half ago. The 70D was the last pro/semi-pro body introduced by Canon before it was introduced.
The 70D has the same basic autofocus system that the original 7D introduced way back in 2009. I shot with the 7D for 3+ years and the shot-to-shot inconsistency of the AF system was that camera's achilles heel. I've been using a 7D Mark II for about a year and the AF system is much closer to the world class AF system on my 5D Mark III than any other APS-C camera I've ever used.
The 7D Mark II also shoots at 10 fps compared to the 7 fps of the 70D and can shoot twice as many raw files before the buffer starts slow down the camera. (31 vs. 15). With a fast card you can pretty much shoot JPEG until the card is fill or the battery is dead without being slowed down by the buffer!
Another advantage is the 7D Mark II's 252 zone RGBir light meter that meters red, blue, green, and near infrared light independently compared to the 70D's 63 zone monochrome light meter. Not only is the metering more accurate, but the color sensitivity capability of the light meter is actually harnessed to assist in tracking moving subjects in AI Servo AF mode. The two Digic 6 processors handle all of the data bandwidth that requires. The 70D has a single Digic 5 processor under the hood.
In addition to the much better AF performance, metering, and faster handling, the "anti-flicker" feature is worth half the price of the 7D Mark II! The camera syncs the shutter to release when flickering light sources at 100hz or 120hz (or their harmonics) are at their peak. It supposedly slows down the maximum frame rate just a hair, but I still get 9+ frames per second shooting at ISO 2500!
- Because the lights are at their peak when the shutter is released, depending on the particulars of the lighting in a specific venue I can actually shoot anywhere from 1/2 to 2/3 to one full stop faster and still get the same exposure levels I got previously when I set exposure based on the average intensity of the lights rather than their peak. In the same stadiums where I once shot at f/2.8 and 1/500 second, I can now shoot at 1/800 or even 1/1000 second at the same aperture and ISO. Many times this is the difference for what I shoot between freezing the action and having the feet/legs and arms/hands of the athlete blurry with their movement.
- By releasing the shutter when the lights are at their peak in the cycle, every image shot in a burst has the same brightness and color. This allows me to apply the same WB and exposure correction to the vast majority of the raw images in post processing. My work flow is no longer bottlenecked by the need to custom color-correct every image separately.
- The consistency between each frame also means jpeg images generated in-camera are also the same brightness and color and much more likely to be usable straight out of camera (when I set the correct exposure).
- With both raw images and jpegs, the entire frame has a consistent exposure level and color. Players on opposite sides of the frame wearing jerseys for the same team actually look like they are wearing the same color!
For more on a case study regarding my decision to upgrade to the 7D Mark II and how it has allowed me to capture more keepers under stadium lighting, please see this answer to When should I upgrade my camera body?