The difference on stock tyres is about 2% I found between ASG's hub dyno and a calibrated DD dyno....which really can be just the difference in the atmo conditions....before my Verso, my XT pulled 253.9wkw on DD dyno, then a week later made 259wkw on the Hub dyno with the same tune.
I asked Sean if there was any real difference and he said if your running stock wheel/tyre combo there is bugger all difference between their dyno and DD dynos BUT running an after market wheel does see a bigger difference but only a max. of about 6-7% tops.....so I say those numbers from tasteofchaos are as accurate as any DD roller dyno which is what most numbers are run on.