Blimey celle, in these days of travel "security", don't make waves
! I understand the need/wish/desire to have the flexibility to use two passports as is your right (my wife is in the same boat as you) and we decided early on that in order not to raise any flags that could potentially inconvenience us, that she would always enter the US on the NZ passport and the UK on the UK passport and only have one ESTA - the thought of having two in the system then using different passports as and when you feel like it would be too much for CBP, certainly at SFO imho, as they can barely cope with one passport, one ESTA.