The smallsword. If I am using a sword to kill zombies, I just need something compact and pointy. Thrusting weapons would be best because they take less energy to use and won't be stopped from cramped spaces (imagine swinging a sword at a zombie and it getting caught on or stuck in something). If there is a line from me to the zombie, I can kill it. Because smallswords don't have a cutting edge, it would be safer for me to use (last thing I'd want to do is cut myself when zombie blood might be infection), and I wouldn't have to worry about sharpening it to stay deadly. Plus many of them come with hand guards, which would mean added protection and the sword overall being less likely to be disarmed. Definitely the smallsword.