[Def]

I have an '06 G35 Coupe(sport package, rear active steer, premium pkg, 6 speed etc.) - nice ride, and while it's a bit heavier than a Z33, they drive very similar.

My thoughts:

-My S13 is probably less than 2500 lbs now, that's the first thing I notice between it and my G35
-G35 rides way nicer while still handling ok. Not quite as razor sharp as the S13, but the S13 doesn't have much(if anything) stock in the suspension anymore. Stock S13s feel like a marshmellow, so no comparison there either.
-G35/Z33 makes better sounds than an NA KA S13/S14, and I'd still say better than an SR'd car. A hot start even with the stock exhaust is nice. I probably get at least one person a month saying something about it sounding nice when I start it up, and it sounds pretty good at some RPM(very quiet at others).

The main thing is the weight - if it's a "fun car" for you, then I'd definitely think twice about the switch. It just isn't as much fun driving a car many hundreds of pounds heavier with all things being equal(power, handling etc.).

If it's more a daily driver type thing, then I say go for it, they're nice rides for sure.