I think that given the choice between the two I'd pick the Ninja, but I've yet to see a CBR250 in person. From the pictures I've seen the attention to detail on the Honda is amazing. It just looks like a more expensive bike compared to the Kawi. The instrument cluster is a glaring example. The gages on the Ninja 250 are one of the few things I don't like about my bike.
Also, I'd like to add that I'm glad that Honda chose to go with a different engine configuration than the Ninjette. I'd hate to see the sporty 250 class of bikes end up like the 600&1000 supersports. Where the bikes are all damn near the same. Also it looks like the Ninjette is a bit quicker than the CBR, and everybody knows that bragging rights are important.