You're right!
It seems faster on other websites (not far though).
The 390 is faster is most games compared to the 970 and is about the same in the ones it doesn't win.
http://www.eurogamer.net/articles/digitalfoundry-2015-amd-radeon-r9-390-8gb-review
Anyone with sense would not get a 3.5GB 970 over an 8GB 390 nowadays. If the 970 was cheaper then go for it but it's the same price as a 390. The 390 is a decent chunk faster in the DX12 benchmarks we've had so far so expect future games to run better on the 390 overall.