Depending on whether or not the term of the loan is lengthened new is always more desirable than used IMO...especially when it comes to performance cars and warranties.
I mean, just because the previous owner of your current car claims to have "babied" it and never driven it hard, that does not mean she didn't do some unforeseen wear to the engine by driving it/maintaining it incorrectly (loading the engine while at low RPM or even filling it with 87 to save money).
I don't know that I would ever feel comfortable buying a used performance car (jut a personal quirk of mine I guess) so depending on the deal that the dealer is willing to work out, it might be worth your while to consider it.
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