What is the difference between these 2?

99-07 Silverado GMC Sierra 1500 Header+Resonator+Y Pipe:eBay Motors (item 170356486024 end time Dec-07-09 14:31:12 PST)

99-00 01 02 03-05 CHEVROLET SILVERADO LT HEADER+Y PIPE:eBay Motors (item 190338716295 end time Dec-29-09 13:02:50 PST)

I am trying to decide between the LPP and OBX. Can't afford Dynatech, Stainless Works, etc...