Don't believe the pipe... or hype, i am running Arion 3.0 beta on WS with two gtx780cards it's not even close when you compare it with corona on i7 4930k(speed to noise ratio).
It has it's usage on product viz or exterior(it supports everything and everything is working dispersion caustics are very good) but some things are not comparable. They menage to gain some speed-up when you compare it to older versions of Arion(most because of new SDK from Nvidia, new cuda, new drivers... Wouldnt go that far and say that speed up isn't credited to Arion developers but lets face it, memory management and general cpu to gpu communication is far better now then few years back...
There is also mtl converter, camera, light, fur, scatter(all Arion default development) still retarded material preview that doesn't show anything as they have nice active shade that is same as production render. It's not about making them look bad(they giving their best i guess) they have partnership with nvidia and right now it is tight race in GFX business. You need Nvidia to run Arion but you don't need Intel or AMD to run Corona, you are free to pick platform you prefer(per per watt) type of situations etc.
Corona look awesome when you compare it to Arion, but still lacking some fundamental things and cuz it's alpha it wouldn't be fair to compare it to other renders right now. Beauty is that is more and more functional as time progresses. But you have to wonder, is it graphic industry doing slow development on purpose for 3rd party SF makers or Corona devs. are fucking GODS when they menage to make something working much faster on something that should be 8-10times slower(GPU vs CPU)...
BTW. i am not saying that Corona is not for product viz etc. far from it. It's even faster but it doesn't have multi-layers, disp etc... and that is only reason why i am using Arion, or Vray.
So far is 2gtx for arion... around 1.5k euros and 600 or 550 for Arion License... and bitterness.
And Corona 0 to stir this pot of "fair developers" and let's say that someone even sponsoring it or god knows what kind of crazy theory but when you draw line it has bigger potential right now and it gets job done 95% of the time.
God knows whats next year hiding.
Cheers