This is one of those issues that whoever answers, typically says what they bought is the best. The numbers on the Prius vs. the Civic hybrid is not anywhere near as clear-cut as the Prius-owner above want you to believe. The Prius gets slightly better mileage in town but the Civic may get better mileage on the highway. Realistically, though, both get better than 40 MPG, so the minor mileage differences are really insignificant. Prius tends to get worse mileage in cold weather, the HCH does better in the cold. Summer temperatures reverse this.
The big reason we chose the HCH are the horrible seats in the Prius, the non-telescoping steering wheel, an the fact you can't use the nav system when driving. The Honda nav system is also more user-friendly. Some folks like the hatch on the Prius, but most american drivers don't like hatch-equipped cars, as shown by sales. You have to decide if a hatch is important.
Also, we got a $2,200 tax credit on the HCH, I think it is down to $1,800 or so now--check W/IRS site.
Altogether we saved over $5,000 compared to a similarly equipped Prius, which we could never make up in any possible gas savings.