Hi Wimpy002, We have owned a 2006 125 Kawa eliminator and currently own a 2006 GZ250. I am 5`10" tall weigh 175 lbs. My wife is 5`4" and weighs about 100 lbs. We always ride two up so here you go:
Kawa 125 pros- Great gas mileage (about 83-85 for us), Decent sitting position, Lightweight, looks bigger then a 125 with the large tank, easy to change plug and oil (On the GZ you have to remove a cover to get to the plug. Not a big deal but wanted to mention it). That pretty much is the pros.
Kawa 125 cons- Battery is a pain. Have to remove it to check water levels and because it is a lower AH battery then the GZ it does seem like it struggles a bit in the cold. Battery upkeep on the Kawa was my biggest pain. Lack of power, even on small inclines we sometime felt like we had to get off and push it. Not much power from the Kawa. While the seats are OK, after about an hour you really feel like you've ridden a 125. Longer rides then an hour really make you feel it. In the cold, you have to fight with the idle, it does not idle very good compared to cold and warmed up. On the GZ I have the idle set in one setting that is perfect and I have not messed with it for some time. Side cover removal of the Kawa was VERY tricky. Not very easy to line the tabs up. Tires for the Kawa you had to get from the Kawa dealer as they are a special size. Even other dealers who said they could get any tire admitted that the 125 Kawa had to get 1 special tire size only. I don't remember the sizes, but we had both the tires, tubes, and rim guard bands done and it was about $300-$400 I believe. As far as additional lighting added, be careful. With the smaller battery (maybe they have a different one in there you should check to make sure), it would be OK. I would be careful on this one.
GZ250 pros- More comfortable, much more power for us, we do not feel like we have to push this anywhere, with the exception of the spark plug, easy upkeep (removing the cover is not bad, just another step in changing the plug), and easier to add on backrest, saddlebags, etc. Also MPG on the GZ for us is about 73 mpg.
GZ250 cons- The only real con I have seen is that some of the GZ's 2005-2007 according to this site:
http://www.automd.com/tsb/bulletin_b223487/
Ours fell under this TSB and what that is the rear tire rubbed on the chain side of the bike. When you looked at the bike form the rear, the fender was way offset to the right and the tire was offset to the left. Our dealer fixed this for ours, but to be honest I still had to do a little mod to it. Being a 2002 yours should be fine but check the back tire/fender anyway. Hope this helps you. GZBrian