Ok, I will try to explain this the best I can, but I am no expert, so if I am wrong, someone correct me.
Shorty Headers will give you more top end power, and are a lot easier to install. Long tube headers are a pain in the you know what to install, but supposedly can give you more power as you do more mods later on. If I was you, I would go with the shorty headers as they are easier to install, and probably alot cheaper than long tube headers. Just be sure that the Jet Coating on the headers is good quality, so that it will not get warped from the heat. Some good header manufacturers to check out are JBA Headers, and BBK. Hope I was able to help you out.