I haven't driven the Mark X, but if it's anything like the Lexus IS250/IS350, then the Toyota Camry is MILES better.
IS250 is horrible on power delivery- I mean you've got a V6, but it feels like each piston weighs a ton and it takes 2 weeks for each revolution. The ride's stiff when it shouldn't be, and it's been screwed with the WORST steering feel ever.