Maybe they were actually different bobby and you just didnt realise it? So many people claim to know that they havent burnt something and that they have done everything identically. Well, sorry, but I dont believe it. There are far too many posts here to demonsrate otherwise 
I went out with the intention of making them identical. I believe that I was very accurate in doing so (there is nothing to suggest that I was not) and conclude that the base sauce used effects the overall result quite dramatically.
Isnt the main difference between the two bases the absence of tomatoes on Darths base (which he adds at the madras stage)?
There are many differences and I could not say what the main one is. Probably the one that yields the most different result but having only made each base as stated in the recipe, I could not possibly speculate.
And did you add the minimal amount of oil in Darths or the increased amount?
I used the increased amount. The thickness of the Darth base means that it does not lend itself to oil separation, unlike the Saffron base.
Because, from what I can tell from your Bhuna photos, the main differences are the redder colour (tomatoes?) and oiliness (oil? haha) of the one made from the saffron base?
Like I said Rai, the thicker bases tend to hold the oil more, whereas a thinner base such as Saffron lets the oil separate out more easily.