If given the option, which recent US presidential election would you flip?

Again, it's not how "obvious" it is, so much as the general logistics of it being something to feasibly worry about. Under the popular vote, in order to rig the system with fraudulent votes, you would need to coordinate a massive effort to somehow inject over a million unexplained votes into the system, and at that point, that is a cumbersome effort that would require a great deal more effort and skill than any political party actually has.

But under the electoral vote, not only do you have situations like Florida in 2000, where the popular vote in the state came down to a five hundred vote difference (something small enough that it could theoretically have had fraudulent basis, without raising a red flag)...but you also have completely legal situations where if the right party has the right man in a position like statewide election commissioner or secretary of state, they can purge the voter rolls, or decide certain votes can't be counted, and that in and of itself could swing a result, given the narrow margins. It only takes one person, acting independently in that situation, rather than any sort of complex and coordinated effort.