Which of these cars is the best?

I am partial to the Impreza, because Subaru is known to be at the forefront of AWD technology, and the best AWD Japan has to offer. Its symmetrical AWD offers traction, balance, and responsiveness that the other Japanese makes can only imitate. If you can't afford Audi for AWD, then you go to Subaru.

That aside, the Impreza was completely redesigned for 2012, and is the most fuel efficient of the 3 models you listed. It also has the highest cabin space (even though the Juke and Matrix are wagons). You'll be getting a lot of new car for the years to come, savings on gas, modern perks in technology, and interior space.

My second choice would be the Matrix, solely because it has the most cargo space (20 cu. ft. vs. Impreza's 12, and Juke's 10). If cargo space is not important to you, then get the Impreza.

I can't think of any reason to get the Juke, unless you are a Nissan fan, or want to spend more money, both on car and gas.

The current generation Matrix was released in 2009, while the Juke came in 2011, so they also aren't as spanking new as the Impreza.

Nissan Juke

Look at Consumer Reports magazine. Your local library has them.