Around $10,000 to spend on a used car. What should I get?

Between the two I'd probably go with the TL. Both were rated about equally reliable by Consumer Reports. WRXs are often modified and are much more likely to have been raced by the previous owner than the TL. Another car to consider would be the RWD Infiniti G35 (also reliable according to Consumer Reports), although it's slightly more expensive than the TL.