I have owned an '03 996TT, '05 997S, '07 Z06 and currently own a 2011 Grand Sport. I will attempt to be as succinct as possible....
911 - fantastic steering/communication (better than any Vette..including the ZR1), wonderful handling, very tossable, nice quality interior, paint and build quality is superior (although my 997S was a rattle trap), noisier and less compliant ride than the C6 Vettes and M3; nowhere near the storage space as a Vette or M3. Personally just not a fan of the exterior styling anymore; performance in the 997.2 version is enough for street driving.
C6 Vette - Vettes have very light steering feel (I personally prefer a heavier feel) with a touch of vagueness, fantastic handling, cornering at on/off exit ramps is absolutely a dream...flat as can be, not as tossable as the 911 though, effortless clutch, better stock shifting, sh!tty non supportive seats; even the 4LT and/or 3LZ (Z06 and ZR1) interior that has the leather dashboard and door panels, is a big step down from the M or the 911; the car is wide with a long nose and really takes some getting used to from a seating perspective. You have to realize from day 1 that the car is not European build quality. If you can accept that, you will probably really enjoy the Vette.
Having said what I said --- I'm 99% sure I will be buying an E92M3 in the next six months to replace my Grand Sport. I thought I'd be OK with driving an SUV ('04 4Runner) as my DD and driving the Vette as a "fun car" but I am getting tired of it already after just 6 months. This is where the M3 is absolutely perfect.... get to drive something that is great fun as a DD (save for crap weather/snow days) and 95% of what the Vette and 911 is from a performance standpoint (remember, we are talking street legal driving...not the track). I know there are those that DD a 911 and Vette but I damn sure can't/won't. Tried to with the 997S....too damn noisey and cramped.
Your last comment mentions tossability, lazer like reflex and steering feel.......the 911 would be a better fit than the Vette or M3 for you for sure. Like others have said, don't discount the CaymanS/R