Hate to rain on this old thread, but the VW polo doesn't get anywhere near 71MPG.
People can barely get 50MPG!
2012 Volkswagen Polo MPG Reports | Fuelly
Maybe someone else can point to other real world MPG numbers that are higher?
You have to keep in mind those MPG estimates are not EPA estimates, a less real-world testing method is done on European cars. Also you have to take into account that imperial gallons are 20% more than USA gallons.
I'd personally take a Prius C over a Polo in the USA.