I haven't driven a Mazda 6, but I test drove its little brother, the Mazda 3 sedan, while my cx-5 car was getting serviced.
Due to the lower center of gravity and lighter weight I was expecting it to handle better than the CX-5, but I came away from the test drive unimpressed.
The dealer let me take the car out without a sales person, so I got to drive the car on the same windy roads in the Santa Monica mountains that I frequent in my cx-5.
I wasn't familiar with the 3, so that probably contributed to my impression, but to me, the CX-5 feels better when driven spiritedly than the Mazda 3.
It might be partially due to the brand new tires on the 3 vs my cx-5 with 39k on the rubber, but the Mazda 3 just didn't feel as fun. The 3 was definitely more planted and I probably took the corners faster, but under-steer was more noticeable and the car just didn't feel as "right" as the CX-5 does.
I disagree.
The 3 (hatchback, in my case) handled better than the CX-5. It feels much more stable and flat in turns and its lighter weight is definitely a big plus.
However, when it comes to ride quality, the 3 does have more road noise come into the cabin, especially coming from the tires.
I never drove the 6, but I believe it would be as good as the 3 but with better ride quality.