I believe the general consensus is that BLF is only better than the Creche on fights where it can hit more than one target.
BLF does scale with your attack power however, and with Unholy's immense amounts of attack power, I wouldn't find it obscene if BLF turned out to be BiS even on a standstill single target fight. (such as Ultraxion)
BLF(and all of the proc trinkets) are amazingly OP right now. an arms warrior in my guilds 2nd group has it and it did ~9% of his damage on zon'ozz, and my resto druid alt has the healing trinket, and it regularly heals for 8-9% of my healing on fights like ultrax, zon'ozz, yor'sahj, or madness. so they are probably a bit under if not on par with the DW weapons depending on class/spec.
Originally Posted by tkjnz
If memory serves me right, a fox is a female wolf.
To be honest the difference between Creche and Fetish is pretty minimal (unless the fight has a hefty amount of adds/aoe damage in which Fetish becomes exponentially better)
Personally, I would use Fetish, as it's proc is kind of...self sufficient, meaning it isn't "wasted" if you're experiencing a period of being rune/runic power starved. If that makes any sense to you. Having said that, they're both fine to use and neither are really the "wrong" choice.