personally, I think the Mz3 sedan is decent, it's not as much of an eye-sore as the hatch. But the hatch is just ass ugly. Looks like the illagitimate love-child of a matrix and a pt-cruser. When I was out car shopping I saw the 3-5 at the same dealership I eneded up buying my P5 from. I didn't even bother to test drive it because of its looks.
However, I have heard from people who have driven both that the P5 has more road feel, which IMHO makes it more of a 'drivers' car. That makes all the diference to me. If I was going to spend the extra money for a brand new car, and I wanted a cushony feel, I'd skip the 3 and pay the extra for the 6. I just love the feel of the ass end of my car starting to slip, ever so slightly, as I'm going 40 through a left hand turn at a stoplight. If you try to make a car too "comfortable" and "fancy" on the inside you loose that.