Canon 760D or 70D, which is better?

I was debating whether to replace my Canon EF-S 18-55mm IS II with the latest EF-S 18-55mm IS STM, because i often use a circular polarising filter for automotive photography and the front of the 18-55mm IS II rotates while focusing which can be quite inconvenient. I have done some research and to buy the new lens it would cost me £80, and i can sell my current one for about £35-£40.

However it occurred to me, that it would perhaps make more sense to just upgrade my entire camera in the process. Rather than buying the new lens individually, i could sell my four year-old Canon 650D with the EF-S 18-55mm IS II for around £350-£375 and purchase something newer with the EF-S 18-55mm IS STM. Unfortunately, my budget for the new camera is strictly limited to £500 as i would like to complete the entire upgrade for less than £150.

After researching the latest Canon range it doesn't seem like i have much choice within my budget. I don't mind buying a used camera providing the shutter count is relatively low and it's in decent condition. It seems to me like the only choices would be the Canon EOS 760D or 70D; but not the 750D because i'd like the additional LCD panel. The 80D, 7D Mark II and 6D are hopelessly out of budget for me, which is a shame.

So the question is, would the 760D or 70D be the better camera overall, and which would be better for someone like myself who enjoys automotive photography? It is quite difficult to find decent comparisons online and i'm not entirely sure what the practical differences are between these cameras. I know the 70D is from the more 'premium' range above the 760D, but the 760D is newer and seems to have competitive specs.

Also, i'm worried that the 800D release will be upcoming within the next few months, is this likely of happening? I would like to purchase this new camera before the Goodwood Festival of Speed which is in about a month's time, but would reconsider if a new camera release was imminent.

Cheers!