Since I own both here is my unbiased opinion. I didn't have it when my stang was stock, so I don't have any back to back runs both stock. But the Z has an outrageously steep rear gear and transmission gearing. I guess it's equal to about a 4.10 in the stang. 6th gear in my Z is the same as 4th gear in my mustang and I have stock 3.27 gears,by that I mean the speed at a set mph is the same rpm in both cars (6th in Z, 4th in stang). So the Z definetly feels faster than a stock stang. But overall I think its close, but If I was driving both cars I think I would be faster in the Z. Like others have said it's really a drivers race, if you drove both cars I think you would probably agree that the Z probably has a slight edge. If the mustang was allowed an equal rear gear, it would probably even it out about exactly. It's not far behind on torque and it's got 27 more hp than a stock stang. But to be fair I don't think these cars can be judged as being in the same field. The Z just inspires confidence on the back roads. It handles like nothing I have drove before. My wife can walk off and leave me on the backroads and my stang has 400rwhp and eibach sportline springs, konis, front strut tower brace, 265/35ZR18 BFG G-Force tires, and the Z is bone stock. But the mustang is definetly a better strip/street car. With the independent rear end in the Z if I launch hard at all it wheel hops so bad it feels like the cars is coming apart. For me the Z doesn't really needed to be modded, it's a high dollar car that is good out of the box and just needs to be driven. It's a great 2 person road trip car, it's got great power, excellent gearing in the transmission, it's superstable at high interstate speeds and is very quiet plus It's a terror on the backroads, it feels like it's on rails.