Ceramic or Stainless Steel

Several questions actually. I'm planning on getting headers and a cat-back for my 94 civic. Looking at the price of headers, I can get the ceramic ones for $270 but the stainless steel ones costs $340. Why the large price difference? Is it because the ceramic ones do not last as long? How long will they last before they... rust??? Which is preferred? Also, does it really make a big difference if I get DC Sports or Greddys? I figure they would provide the same hp boost. I'm going to get Greddy SPs. Can I install this myself or who it be better to have a mechanic do this? I don't know if the cat-back can just be installed w/o twisting the pipes, etc. Thanks.