Sony seems to be about one generation ahead with their sensors for stills
I disagree. Have you not seen the DxO charts that show 5D3 substantially better than D800 at pretty much everything greater than ISO 2400 (or lower for some stats)?
If you want the best high ISO camera at this price tier, 5D3 is a no-brainer. It's as much better at high ISO as D800 is better at low ISO.
So how can you argue Canon is a generation behind in sensor technology?
Not sure if this link works, but if you compare the 5D III and the D800 there is a huge gap at low ISO (in favor of D800) in almost all measurements. However, I don't see the significant advantage of 5D III over D800 with high ISO - it is slightly better, but it's not a significant difference. Could you please let me know on which measurement the 5D III really beats the D800?
And yes, as a high ISO camera the 5D III is probably better, but as an overall camera the 5D III can't hold a candle to D800 (at least from a scientific measurement standpoint).