Sounds good to me, but the real answer might be that either would work equally as well. It really depends on the peak switching current levels required for the circuit. Once you know what the peak current demands are you should then be able to calculate if it approaches the core saturation levels of either core. It is possible that neither core will work if the current demand is too high. With incomplete data only guesses, hunches or assumptions are being made. It is first and foremost a calculatable engineering task.That's a point I didn't think about at all. Not sure how to calculate it though, and will have to do some research.
One core has a saturation flux of 4300 (8 turns); the other is 2350 (49 turns). I'd guess I'm still better with the 8 turn core.