Why do you say there are only two approaches? What about "the long cook" with little oil and "the quick cook" with lots of oil?
Surely no BIR truly uses a "quick method" of making a base DD (except in desperation perhaps!)! It's obviously variable! They make stacks of base, for the session, and it invariably sits there, for several hours on end!
Anyway, to answer your question (and, yes, I have tried all 4 options)..obviously it's a question of which results in the oil absorbing and distributing the most amount of flavour from the spices throughout the curry. Therefore, the longer the oil is in contact with the spice the better!
So, to my mind (for a BIR at least), it's lots of oil in the base for a long time. AND not skimping on the oil in the final curry!