I could be mistaken but you're going to want to know if it's a Challenger 180 or a 180 SE. The 2009 180 SE is 255 HP while the 2008 180 SE is 215 HP. The 2009 180 (no SE) is 215 HP while the 2008 180 (no SE) is 180 HP. So without the designation you could theoretically be comparing a 255 HP boat to a 180 HP boat!
I think too the 2009 has an upgraded stereo and some upgraded finishings but yes the biggest difference is the engine and the paint job. Heh, if you're new to jet boats like I was last year then I can assure you the 2008, which is mostly white, is a pretty easy buff for those early docking "learning sessions". Not sure you'd find the same with the full red or blue like the 2009s.