I juggled this exact decision about 6 months ago. For many reasons, I went with the 85D. Range, as everyone has pointed out, is king. If there is ever some battery degradation down the road, you want to start out with as much as you can. The other reason, which is more subtle, is that the 85D will actually charge quicker on the superchargers since the battery is larger. This isn't intuitive to me, so I did some research and you can find videos of the different sized batteries charging and the larger the battery, the faster to the 80%.
Plus, I've got to admit, I was not that impressed with the 70D acceleration. It was fast, but for $80k it should be much faster.