The main difference is that the 2011 WRX has the STI styling (widebody)... the increased track means it has better grip. The wheels are also bigger (17x8 in) and so is the tyre size. Everything else is pretty much the same.
The engine is exactly the same with no increase in power. Oh and bluetooth is now comes standard. I believe the cost is exactly the same.To most people the differences are very subtle and if you don't mind buying second hand you would probably get more value out of a used 2010 one.
I believe for the price of a new 2011 WRX you could probably get a 2009 STI which has a lot more power.
Cachemoney! Researching a bit on Google, I found a very good comparison sheet for the Subaru Impreza WRX on the Subaru website: subaru.com/content/static/vehicles/impre... There are many options to compare! I remember that I wanted such a comparison from an older model car to a newer model myself and so I walked into the showroom and asked one of their sales men.
Wow! He just rattled off all the differences at lightning speed and didn't stop for catching a breath for at least 1/2 an hour (ok, I'm exaggerating a bit! ), but these sales people get trained on exactly that.So why not take a stroll down to your Subaru dealer and get the all the real differences between the 2011 Subaru Impreza WRX and the 2010 Subaru Impreza WRX straight from the "horse's mouth"?
Hope this helps!
Get a quick look at the trade-in value. And if you already own a Subaru, you might be eligible for the Subaru Guaranteed Trade-In Program.