well theoretically, with lower asic you have more leakage thus more volts flying through the entire chip. Since ln2 can take care of the heat from the leakage, your main problem would be voltage consistency throughout the chip (something you cant really control) so what ends up happening is you need more voltage (thus the higher stock voltage) to keep a consistent clock. it is the opposite for higher asic/lower stock voltage. What tends to happen is if we were to plot out each cards stats on a graph, somewhere the two lines (cards) voltages/clocks will cross (id say around 1500 core clock) now, what many people believe is that the lower asic will prevail because of the extra leaked voltage that actually helps you attain higher clocks at those speeds/temps since temperature would be the only fixable problem. I have not gone and dis proven this personally, but talking to many ln2'ers, the higher asic is actually better in the end because the silicon itself provides a more consistent delivery of power, whether its higher or lower voltage, so those chips can handle the highest voltages (1.6+) more successfully and in the end, provide better overclocks (though they will most likely take more voltage to reach the highest overclocks)
honestly, asic is a small piece of the puzzle, its all about the nano sized channels of silicon and how well they are structured in the chip itself. This is why the lighting goes to strides to condition the voltage prior to reaching the gpu (and why they achieved a 1800 mhz clock as apposed to the 1700 previous record). the more consistent of power he chip uses and produces, the better chance you have, thus why i believe higher asic is truly better than lower when using ln2.