I'm not convinced it makes much difference. I also have two, and I've travelled on the "wrong" one before.

Do we know for certain whether when you enter the US, your data is matched against the API recorded for the flight you say you entered the US on?

IMO it's more likely that the API is just used to check you against the various blacklists before you travel, and the immigration process when you get to the US and hand over the I-94W (which of course is checked against the passport you hand over with it) is likely to be independent of that.

Of course, I'm not in any way advocating risking it intentionally...!