Zoom Zoom vs. Fit Is Go?
From my own experience the stock Fit handles awesome! Even with the crappy stock tires I can take turns pretty quickly and feel relaxed. Steering is very responsive and when you turn you don't feel a heavy weight shift. So far I love the car's handling.
I'm keeping my car stock, but most people on this site tune their suspension, so I can only imagine how much better the Fit would handle.
My old roommate has a Mazda 3 hatch and it's super nice. Leather interior, navi, HID's... Only thing is that it does seem like it's a bit beefy and heavy. The Fit isn't super light either, but it handles like it is.
Check out these reviews:
Mazda 3
Mazda 3 - Road Test/Budget Rides/Car Shopping/Hot Lists/Reviews/Car and Driver - Car And Driver
Honda Fit
2008 Honda Fit Sport - Feature / 2008 Honda Fit / Fit / Honda / Buying Guide / Car and Driver - Car And Driver