I've never owned a 4th gen but have driven a few.
5th gen definitely feel heavier and seem more comfort than sport orientated.
More space inside, with much more legroom for the rear passengers. My 3.6R has over 230,000km now with no major faults in my ownership *touch wood*.
That being said, they're a great car for the money; comfortable, great factory audio, well optioned.
And they can still be driven in a spirited manner, just opt for grippy tires and "sporty" brake pads.