Depends on what you want. The Z is a more sporty experience in just about every way, but especially in appearance. Look at the Z's roofline and the G's. Park two next to each other and look at the height. Look at the fender flares on the Z. Then decide which car you like more. Some will drool over the G, others cannot live without a Z.

Next open the door. Look at the interior door panels - the Z's is sporty with aviator-style air vents, artsy door handles, and a shapely curve. The G's is nicely finished with contrasting trim, but very traditional. Door handles similar to a 96 maxima (although finished more nicely), normal air vents, etc. Now look at the seats...the G's look really nicely finished but lack the bolstering of the Z's seats. Then you can look at the center console...the G's has a nice metal finish, but it's pretty cluttered. The Z's finish is definitely not as nice here, but the Z makes up for it with its triple pod of gauges and its ease of use.

Now sit in the car, twist the key and drive off. After about 15 minutes you'll see the difference. The G is softer (still somewhat firm mind you) and tends to lean a little more in curves. It feels a little heavier, a little less nimble on its feet. The Z turns in quicker and feels more planted - but at the expensive of noise and ride quality (thank you crappy RE040s).

After an hour of driving each you'll know what you want. The cost difference, when similarly equipped, is not really a constraint for most people.

Now you've got your homework, go and do it!
NzZ