What year Scion tC is best (2005, 2006, 2007, 2008, 2009, 2010)?
If used, the one that was maintained the best, and has receipts to prove it, and is within your budget.
Newer is always better since there is not as much time for neglect to rear it's ugly head. This goes along with bscar's comment.
No real difference. Newer is better, lower miles is better (a little), but good maintenance records are the MOST important.
This car appears to have change very little but has made some subtle improvements in standard equipment. The newest.
When dealing with a car like the Scion, thee best way to make a purchase decision is to buy the one with the best sounding radio...
One thing to be wary of when considering a used tC is that the car was marketed as being a "blank slate" prime for modifying and customizing. Scion sold numerouus engine and suspension accessories right along with the car, even including them in the car's manual. The car and Scion's marketing approach also spawned a huge aftermarket performance parts industry. Many were modified, not always properly. I'd avoid any that shows and signs of having been modified. It's impossible to tell if it's been done properly.