Having ridden most of the BX boards out there I feel I can give a good comparison and overview on the subject.
1st thing is boards like Donek's Incline and Palmer Channel are very different from BX specific boards like the Madd 168 and the Volkl Cross. The Palmer, Doneks and even Rad Airs are more freeride boards that do ok at speeds needed for BX. I own a Palmer Channel 164 and 156, a Rad Air LSD Reto 164, a Volkl Cross 167 and 160 and a Madd 168 BX and Madd Freestyle 158. I have also ridden a Incline 164 about a dozen days.
Of the Freeride boards I find the Palmer the best for BX. the titanium top sheet makes it real damp and it handles ruts pretty well. I find the RA Reto to be bad at speed. It gets real twitchy. It is one of the most fun boards to play on and reccomend it if many boards is an option. The incline is middle ground between the two.
Onto the BX boards. If BX racing is your fancy the other boards can't compare to the Madd or Volkl. They are not the most versatile and are really meant for fast obstacle laiden courses. The Volkl feels a little more responsive. It is not as fast or stable at speeds as the Madd and feels shorter than it's length. The Madd is superior on ice, crud and at speed. It does make you ride it, though! If you are new to BX and ride mostly alpine I would reccomend the Madd, but if you are new to BX and have mostly ridden freestyle set ups I would reccomend the Volkl.
One other note is that the Madd Freestyle 158 is a good board for short, technical BX courses. It has the Electra 4000 base and is probably the fastest non-alpine 158 on the market. This board is allowing me to sell my Reto and Palmers!
I have compared almost all BX boards out there so if you have any BX specific questions please feel free to email me.