A lot of times, a softer suspension, plus a more equal weight distribution, and a longer wheelbase means better times on the track. The 350 may be able to pull more g's, and stop faster, and accelerate faster, but the G may be a more balanced machine, overall. Balance allows the car to keep its speed up throughout the track, and not wast energy and time in oversteer, understeer, and harder braking.
I recall the Brembro brakes are standard on the G, and with the aero package, the G is more stable, at higher speeds. I seem to recall the G stopped shorter.
I believe Car and Drive did tests on both machines. Although not against one another, but I remember them being suprosed with the results.
Either way, you can't loose.
I see two to three 350's a day, and one to two G's a month, around town.
I prefer to be part of a smaller crowd, when it comes to cars. That is what I like about the Q, there are a few around, but mostly are 98 to 2003 models.