Sorry I read it that the fuel consumption comment was separate and that the remark was purely pointing at performance. BMW cite the 40d as running 37.7 mpg (sorry for the imperial measurements - typical Brit!) and 50d at 36.7 mpg.
To me, the additional 75bhp and full second off the 0-60 mph dash is worth 1mpg - would you not agree?
As for 'better' that, again, to me meant improvement in the development of the diesel powered vehicle to bring it up to a level of parity with the larger petrol engine (but with better mpg). BMW cite the 50i as giving 22.6 mpg for instance. That equates to [the 50d giving] over 100 miles more on a tank; yet with the same base performance figures.