To have fun and play around with short spurts nothing beats the burn outs, drifting and raw power of a z28 plus parts to produce extra horse power for a z28 is easier to work on and lighter on your pockets.
On the other hand civics are fun, they corner well, they drive forever, get great gas milage and are always underestimated because of power to weight ratio.
I have owned both I personaly still own a civic.