You know, it's funny this post has come up because I've been looking at the used Ford Tauruses quite a bit lately. I, too, am thoroughly amazed at what a bargain you can get with one of these cars! There are VERY clean 2006 models all over Ebay with less than 10,000 miles (from Florida mainly - so probably ex-rentals), selling for $11,500 to $13,500.
I normally would shy away from ex-rentals, but how bad could the renters really ruin these cars in less than 10,000 miles? Most people advocate driving it like you stole it during the break-in period anyhow. Heck, these things are still brand new cars in my mind. And the Ford Taurus is a very reliable, safe, and low-insurance vehicle. (It was listed as the "least stolen vehicle" on a CNN.com article I read a few weeks ago.)
I don't know much about the Malibus but I like their styling okay. My mother-in-law has a Malibu with the V6 and it seems like a pretty nice car overall. Still, I prefer the overall look and feel of the Tauruses so that's what I'd probably (and might) buy.
What other 2006 model car with less than 10,000 miles can be readily found for less than $13,000??? Certainly not any foreign brand, and certainly not anything that would be good for a reliable and inexpensive family car. This is what's pushing me toward a Taurus - cheap, reliable, low insurance, decent fuel economy, and a fairly roomy and comfortable family car.
I'm on a very tight budget, so the thought of being able to buy an "almost new" car for $12,000 is VERY appealing!
I say go for whichever one you like the best!