With all due respect to the G35 (an awesome car in its own way) and their owners here, I have to say that I am very glad that I have the M45 and not the G35 we initially went in to buy. For the reasons I am about to go into here.
So, IMHO, if you are considering buying a G35 sedan, please take a few minutes and a deep breath and negotiate a deal on the M45 instead. They are close enough in price (with the deals that Infiniti dealers are giving on the M45) that you will be better off.
(As an aside, the G35 coupe may be better in some regards than the G35 sedan, but I suspect that some of my comments may apply anyway.)
- Interior. Hands down, the M45 is easily way better. The interior has far more of a luxury feel and look. The leather is better, there is far less plastic, far less "high tech gizmo" feel. The shifter is more robust, the seats are wider and longer (i.e., more comfortable), the controls and knobs and switches feel rugged rather than flimsy.
- Driving. The M45 engine is smo-o-o-ooth! At 5k to 6k rpm, the G35 engine sounds noisy and raucous (!) compared to the M45. The revs on the M45 climb easier and the engine sound in the cabin is muted. Vibration is lower. Just a smooth rise in revs and speed when you press the accelerator (do get the transmission re-programming done - on both cars - before you compare). The transmission shifts without any jarring feel - the extra weight of the M45 may have something to do with that.
- Acceleration. Very comparable, but the M45 felt stronger and faster, particularly when the speeds built up over 100 mph. I know that these cars have similar acceleration numbers, but the M45 felt like it was reaching its goals more easily and without any strain. Sorta like "you wanna accelerate? okay, let's roll!" rather then the G35's "you wanna what? groan!" kind of response.
- Brakes. Close call! The G35 seemed a bit more precise and the M45 feel was a bit more mushy. But they both stopped very well. This is one area where the nod would go to the G35, but not enough to make me want it instead.
- Handling. The M45 is sportier than the G35 sedan - on highways and curves. I felt more in control, without bumps on the highway causing unusual changes or twitchiness in the driving line. The tires on the M45 are grippier (Bridgestone Turanza 235/45-18 in a WR) compared to the G35 (Goodyear Eagle RS-A in a 215/??-17). The steering is "lighter" on the G35, but buffers the road feel too much. The M45 steering wheel does take more effort to turn than the G35, more than my 1995 Q45 or my wife's Acura 2.2 CL, but the fact that my wife does not mind it, means to me that this is not an issue!
- Visibility. Surprisingly good in both cars, but the G35 is smaller and easier to see around. So the nod goes there, but not by a lot. I am 5' 10", and am able to adjust the seats on the M45 to compensate accordingly. My wife at 5' 5" did not like my 1995 Q45 ("too big"), but finds the M45 size just fine!