I just got a Z this last weekend. After looking for a while I was in the same boat. I know I couldnt afford a brand new bike but was on the fence also about if I wanted a first or second gen. I never actually looked at a 2nd gen but from the general consensus, and reviews all over the internet message boards the 2nd gen's were kinda a funk years for the Z. Not to take anything away from the 2nd gen's, and I have never rode one so I can't compare the two. I am only stating what I gathered from what I read. You also have people who love their 2nd gens. Guess it just comes down to personal preference.
I personally love the edgy, cut, street fighter look the 1st gens have. There was one close to me for sale, it was in great shape, so I bit on it. Probably could have found a 2nd gen for close to the same price but the 1st gen is what I decided on. I LOVE it so far, Im sure whatever one you decide to go with will be great. I don't ever buy a bike depending on a spec sheet. A bike might handle like a dream and have all the power in the world but if your not attracted to it, and passionate about it every time you open your garage door, its just a machine. But maybe I'm just crazy.