It all depends on your budget and what paint you shoot.
If you have unlimited cash then I would go for the freak, particularly if you shoot lots of different paint. Also the advantage of the freak is that should you change your gun at a later date you need only buy a new back for it.
The Boomstick is a lovely barrel, perhaps go for a second hand one if you can find one in the right bore size for your chosen paint. This way you can keep the costs down even though the barrel is useless should you change to a different gun later.
Or for a budget barrel go for the smart parts Tear drop, AA if you have a little more cash, or the Dye Excel.
Whew, sorry, bit long that one!
Laterz
Ian