ive ridden both bikes and own a 07 demo 8. build quality of demo's is far better than on the sunday (welds,bearings ,paint) ,the retail of the demo 8 is 4900 ,which imo is a great deal with the specs it comes with and the bike weighs only 41lbs stock (i know the wc is lighter ,but costs more). oh ,and there is that little thing that is called - lifetime warrenty !!!
one more point worth mentioning about build quality : every sunday i know had play in the links ,even when it was new out of the box.iron horse didnt admit that there is somthing wrong with the design and instead blamed the shock manu supplying bad hardware.
now, for 07 there is a new "magic" link that solves all that ,but wait a second ,it will cost u 360$ !!! now how lame is that ???
now for the bikes : for me ,the demo suspension outperforms the sunday on any sitiuation and terrain (specialy on long fast terrain) !!! maybe the dw is better at pedaling (maybe) ,but sorry guys ,i ride dh and not am / xc .the demo suspension is alot more active under braking (u can really notice it) and eats square edged hits far better.
(btw , i have three friends with sundays elites that will agree with me on that.)
now ,as far as geo goes , the sunday has a great geo,which really help the bike shine on the slopes for most peapole ,just not for me. i prefer the longer and slacker demo (but it is just me cause im fairly big and like to plow) .
another thing is cornering. well ,the sunday really corners amazing (bc of low cg and bb) ,but i find the demo corners very good as well . its just longer so ull need to put more muscle into it.
both bikes are very capable dh race bikes ,but for me, the demo's suspension ,geo ,build quality and warennty makes it an easy choice.