the 560 and the 6870 will be really close. I haven't seen any benchmarks for the 560 since it literally JUST came out in the past few days. But Assuming it follows the same path as its predecessors, it will be very close and likely better than the 6870. And the 5850 will be the lowest of those 3.
Both the 6870 and the 5870 AND the 5850 have quite a bit lower performance than the 570. The 560 won't be much worse than the 570; therefor, the 560 will perform better than all of those cards. But only time and benchmarks will tell. pipinhot2, that link shows that both the 5870 and the 6870 perform better than the 570, but benchmarks right there prove otherwise. Stats can tell you what the card is capable of, but it can't guarantee the performance.
Yup. ATI will put butter specs because they can, but that doesn't mean it's going to perform better. Never refer to pure specs, ALWAYS look for benchmarks. Those benchmarks just proved that the 560 is by far better than all the 5-6870's
http://www.tomshardware.com/reviews/nvidia-geforce-gtx-... the 5870 is pretty beefy overall....but. the 560 has physx........ they are all pretty close though. If you plan on SLI or xfire later, the 6870 will scale better than 5870. In australia the 6950 ($330) is cheaper than gtx560 ($349) so it would be pretty obvious in that case what you would get. The 5870 ($299) is also cheaper than all of them. really depends where you are and where you can buy from though.
Thats going to depend on who you ask. The GTX560 is similar to the GTX470, which is close in performance to the 5870. (depend on the game and settings used.) I would say pick the cheaper of the two if you're going to run stock, or the GTX560 if you'll be OCing.