Unless you are racing, the differences between the 2007 and 2008 250cc Ninjas are mostly looks and comfort. One looks older and is more comfortable, and the 2008+ has a more modern look, a stiffer stock suspension better for racing, and is less comfortable, especially for someone at least 6 feet tall.
The older one will save you a lot of cash, and you can put extra money into making it look and handle better if you want. If you hire out all maintenance and repair, you might be better off with a newer bike, because an older bike starts needing more and more work and new parts to keep it going and safer.
Here is a part I found for the newer 250cc Ninja, that makes the footpegs higher and further back for racing, or you can switch sides for them and flip them upside down to make the pegs lower and further forward, a better fit for a taller rider, but you will scrape the pegs earlier at higher race cornering speeds (there is a photo of them on the 250 Ninja at the bottom left of the page):