I cannot recommend the Impala more than anything else in the road today. It is an old-school styled, comfy road warrior that has evolved to include efficiency and better than expected reliability for GM.
After renting several of these from the year 2007-2011 inclusive, I have found them to be of unbeatable value and comfort, esp. for the price point. The rentals were subject to +8 hour road one-way road trips with varying road conditions and different drivers (myself and my spouse). Mind you, these cars were all VERY low milage examples.
We found this car to be very comparable in road feel and handling to the Cadillac DTS which we also used for the same trip. Aside from the lack of toys as offered on the Cadillac, the Impala is just as much of a comfortable cruiser as the DTS but without the power of the 4.6 Northstar V8.
One of the downsides I recall from this car was after a trip through the Rocky Mountains. There are some very long and steep roads that require you to use you brakes often, or else you will quickly find youself coasting over 180kph frequently. After using the brakes consistantly, I found the steering to become loose and vibrations when applying the brakes. After I got off the freeway, I found that the lug nuts on all 4 wheels had worked themselves loose. I thought this was a one-time occurance, but it happened on our way home back to Vancouver. Obviously the brakes were working VERY hard as the lug wrench had heated up considerably while attempting to re-tighten the alloy wheels. Mind you, the car should not have had this problem consideirng it was below 10k miles and had hardly made it to it's first OCI.
Below are a couple of sites I use to evaluate cars. The Impala is a very decent car as reported in the reviews. But for it's intended purpose, i can't see it being any WORSE than the Corsica.
http://www.edmunds.com/chevrolet/impala/2009/consumer-reviews.html?sub=sedan
http://www.carsurvey.org/reviews/chevrolet/impala/2008/single-page/
I don't have as much expereince with teh Taurus, but from the reviews and the reliability ratings, I'd seriously consider one over the Impala if the prices were equivalent
http://www.edmunds.com/ford/taurus/2009/consumer-reviews.html?sub=sedan
http://www.carsurvey.org/reviews/ford/taurus/2008/single-page/
good luck! and let us know what you decide on