No major differences, but i'd definitely pick the honda. I used to have a 99 recon, and my brother has an 03 250ex. Both are bulletproof and very fun to ride.

The z250 has a shifter system which involves quite a few pivot points, which makes shifting notchy, and eventually the pivot points will begin to wear and the shifter will be sloppy. The honda has a direct shifter which shifts smoother, quicker, and has a better feel to it.

The 250ex also has better suspension for sport riding. The suspension on a z250 is spongier, and isn't real good for aggressive riding.

Honestly though it might be a better idea to start out with a faster machine like a z400 or 400ex. You can get used to the power of a 250 pretty quick, and the first time you ride with a bigger machine you're probably going to have a for sale sign on the 250. I'm speaking from experience, because after 3 years of riding my recon i was looking for more power, and last year I traded it for my warrior. As soon as I got my warrior my brother started to look for something faster also. You can get a 400 a couple years old for about the price you will pay for a new 250.