i saw both, and watched the 2nd one during the summer in japan. I have to say, the first one is MUCH MUCH better. With the second one, the director passed away half way through the making so his son took over the directing, and you can tell, its quite a different style. Rather than the school survival, its more about using the school kids as fodder for some sad/pathetic war against terrorism.
Not as much blood and gore compared to the first one, but the 2nd one has a strong anti-western imagery to an extent. Wasnt too bad, but its not something i'd watch a few times, unlike the first movie, where i watched it several times, and i still enjoy it. The 2nd one, i cant see if more than twice because to me, it didnt present that much of a fun factor compared to the first.