I work for Hertz Rent A Car and I've basically driven the base model version of almost every new car out right now. I guess I'll give my opinions on some mid size sedans and trucks because I think that's what you're most likely gonna end up buying. Here's a quick overview, and I mean quick...
Mitsubishi Galant: The car's not bad but out of all the sedans listed it's the worst. The engine(I've only driven the 4 cylinder of each model) is the least powerful and most noisiest and the car feels super heavy because of the anemic engine, or maybe it's that the car is super heavy. The interior quality is alright and the ride and handling is alright but the car is just overall boring.
Honda Accord: The car is powerful and the stock engine sounds pretty sweet...but at least for me, I don't like the exterior design. The interior design isn't much better, has a weird shaped dashboard and the center console also looks weird. They tried too hard to make the dash look like the Civic's(which is sweet BTW) but the Accord's is just a mess of angles and weird shapes. The seats are very comfortable and the ride is smooth, not as smooth as the Galant's. The Accord has a slightly more stiffer suspension...slightly.
Nissan Altima: Let me tell you something, I hate push button start and because of this the Altima annoys the hell out of me. I like the exterior design and the interior is also nice, nice but nothing out of this world. The base engine seems just as powerful as the Galant's but it's not as noisy as the Galant's. Still not as smooth as the 4 banger in the Accord, that engine is a work of art. One thing I can't stand...I mean I hate this thing with a passion is the stupid CVT transmission. I would really enjoy the Altima a lot more if it had a regular automatic or maybe a stick
Mazda 6: I LOVE THE MAZDA 6, but...it wouldn't be the car I'd end up buying(If I had kids, which wouldn't happen because I don't really like kids nor want them). The stock 4 cylinder is very powerful, not as smooth as the Accord's but better than the Altima and Galant by miles. My favorite thing about this car is the ride, the suspension is the stiffest but not to the point where it's an uncomfortable car...it just feels very performance oriented(for a mid size sedan of course). All that BS you hear on Mazda commercials about sportiness and Zoom Zoom, well I guess it's true because this car feels the sportiest out of all of them. The interior is very comfortable, well at least just as comfortable as the others, well aside from the Altima, which I think has the most comfiest front seats(I left that out sorry)
Chevrolet Malibu: The only thing I like about this car are the exterior, the interior looks...well...funky. The interior has a mix of weird two tone colors and weird feeling materials(the dash feels like it's made of foam?)...I don't like it. The front seats are the most uncomfortable out of all of them and the car drives basically just like a Chevy Cobalt...it's bad. This car is based on a German Opel/Vauxhall and I expected a much better performance oriented ride like the Mazda's but was seriously disappointed...
Ford Fusion: If I had a wife and kids and had to live with a mid size sedan for the rest of my boring life it would definitely be the Ford Fusion. I can't really find anything bad to say about this car, the ride is somewhat like the Mazda's but a bit more smooth. The engine has good power and doesn't sound like a small tractor's engine. The interior is very comfortable and looks very nice, as with the exterior which to me looks great. Driving this car gives me the same feeling as when I'm wearing a nice suit that I got at good deal at the Men's Wearhouse...it's a good feeling.
Toyota Camry: This car does everything you ask it to do and does it very well. I would go as far as to say it is the best mid size sedan out of all of them, but...it is very boring and will steal your soul like Shang Tsung in the Mortal Kombat video games.
Conclusion: Go test drive a Ford Fusion and feel like James Bond in a cheap suit...it's that good.
I'm gonna go have lunch and I'll be back later to do the trucks
BTW, today is my day off...so it's not like I'm writing these reviews while on company time(just in case there are any of Hertz's many spies lurking the NICO forums)