We test-drove both.
I loved the look of the 300C and with the star grill it got mistaken for something else quite often...
However - it didn't go round corners. Was fab on motorways and dual-carriageways but the first roundabout or twisty bit was horrid. Bad turn-in, roll, understeer, uncommunicative steering, wooden brakes - you name it, it had it. There was no way I could live with it.
Also - and this was on a 200-mile-old demonstrator - the parking brake release handle was broken and bits of trim all over didn't seem to be fitted very well (and this was a corporate demo vehicle!). On top of that, the fake tortoise-shell trim was nasty.
Did go like a rocket in a straight line though.....