New Prius C Two, not II, or CPO Prius of similar price?

I'm purchasing a Prius. Roman numerals were used for model designation for the 2010 model year. I've spent days and days doing research on everything from reviews to pricing, how to go about buying, what to expect at the dealership, etc. I've basically read Edmunds.

My problem is New vs. Used, but with a twist. The best offer I've received on a brand new 2014 (never been driven) Prius C Two is $17,849, and that's before I've even gone to the dealership to negotiate. Other offers I've gotten on used Priuses (Not C's, just standard Prius Two or threes) range from 15 to 18k dollars, between 20 and 40k miles.

Here's my issue: I currently qualify for a boatload of discounts from different dealerships, including first time buyer discounts, recent graduate discounts, 0%APR and "friend of salesperson" (whatever) discounts when purchasing a NEW car. All of these within the context of a standard 60 month financing period. A couple of these are discounts I'm never going to have again. I'm afraid that if I decide to buy a used car that I'm wasting these opportunities. On top of that, the price differences aren't dramatic, or at least what I would consider dramatic. I could be paying as low as $316 a month for a brand new car or the between the same price to ~$270 a month for a used car. This is because on top of the Prius being a more expensive car than the Prius C, I don't get the crazy "new car" discounts I mentioned before, and I don't qualify for 0% financing. I can get 1.99% at the best through the Toyota CPO program itself.

I'm really stuck on what to do. I like both models of car. Where does the argument on New vs Used stand when the cars you're considering are similarly priced? New doesn't bother me because I'm gonna drive this car into the ground; I don't care about eating the depreciation. How much extra money becomes too much when it means getting into a new car versus a used one? How much would I be losing in terms of MPG if I got a 3 year old Prius vs a new Prius C? Even though I get the benefit of Toyota's CPO policy, would it be worth it just from a maintenance standpoint to get the new car or pay a little less for a car I'll have to service sooner? I'm looking for personal opinions as well as objective ones. Thank you so much.

Additional Note: I'm LEANING toward getting a used Prius. If I could afford a brand new regular Prius liftback it wouldn't even be a question, but they're considerably more expensive than the C. I'm a very large, very tall person. The C felt ok during a test drive though.