Ok, first of all, I have owned a stealth for 2 years, and have driven and have vast knowledge of 300zx's and Skylines.
The stealth was a good car, but parts are a fucking bitch. It was way before its time and is sexy as hell, but it has huge downsides man. The engine's are fairly well built, and can handle some decent boost levels and respond ok to modifications which is always good. And yes, they ARE heavy, 3700lbs is NOT fun man. I sold my stealth and that was one of the reasons why, that and parts basically.
When you say skyline I'm assuming your from Canada and your talking about R32's that are being imported due to the 15 yr import law still in effect (and hopefully stays that way). And also, I'm gonna assume your talking about the GTR model and not the GTS-T for GTS-4. If so, were still talking about a 200-300 pound weight difference, but that doesnt really matter. The GTR has so much aftermarket support, and the RB26 responds SO well to modifications it doesnt even compare to the stealths 6G72. It can handle about 500-550 whp on stock internals, and the block can hold over 1 000. When your comparing the stealth and the GTR, were talking about 2 very different cars. 1 is a luxury sports cruising car, and the other is a de-tuned supercar that is considered by many as the king of japanese sports cars througout the 1990's, dominating nearly every competitive track event. Plus, owning a Right Hand drive is awsome man, I own a Nissan 180sx here in Ontario with the ca18 and love it to death. So once again, so many differences I don't even want to get into it.
The 300zx is kind of the middle car here between both of these, having something in common with both cars. Its very similar to the stealth in the fact it is a sexy luxury car, with some guts. The VG30 is even a lot like the stealths powerplant. The great thing about Nissans is the interchangable parts too, which PWNS the stealth, because parts are SUCH bitch to find, and when you do they are expensive as shit. At least with my 180 I can get 240 parts for it.
So yea, in conclusion, I have owned a stealth, driven a 300zx, driven an R32, and own a 180sx, and let me say, don't get over your head on the stealth man, its a money pit. Go get yourself a Honda or something, because your an idiot.