Basically you want something strong, but reasonably light. Frame, fork, bars, and stem are all pretty personal to what feels right for you. Profile hubs are sick, and MacNeil Conjoined cranks are pretty damn sick. Get some TI spokes and Alex or Odessy rims. Intense Micro knobbies are great tires. Do some research.
those two bikes look more like custom builds.
i think the best way to go is to buy a cheaper bike then upgrade it. add new sprocket, tires, rims, fork. thats what im doing...i just bought a eastern lowdown off of danscomp and now im starting to upgrade as i ride...i hope to move into dirt jumping this summer
PM me for an invite to the MUSIC CULT
Andy:Bronson guess what?
Andy: Alot of people told me how messed up we were last night.
Me: Oh yeah. Like who?
Andy: I dunno but I'm guessing we were pretty fucked up.
"People always ask me, 'is it worth it, getting hurt that much?' and the answer is yes, I would do it all over again, have six more season ending injuries in the next 10 years to keep doing what we get to do, there's nothing better than sliding down snow and flying through the air"
--RIP Shane, you will be missed
For dirt jumping/trails the best bikes are those with a slacker head angle, and longer back end/top tubes. The best frames out now would probably be the Terrible One Reuben, Deluxe, Fit Lurch, or Credence if you can track one down.