This is personal preference. The BMX bar will allow you to stand more upright whereas the Dirt Jumper (DJ) will sit lower and naturally get your body weight more forward. In skibiking we need our weight forward over the front ski for several reasons, and some have found that by using the lower DJ bar, you naturally put more weight on the front ski.
On that note, when we cut the steer tube on the fork we do not cut it so that the handlebar stem sits right on top of the headset cap like on mountain bikes. We leave about 2″ of stack height with spacers so you can adjust the height of the handlebar. If you feel like you can’t get enough weight forward, try lowering the bar on the stack.