The hits-to-kill list begs to differ, Decado2.

All-On-Generic, Billhook vs Javelin (Orc Warrior, full helm):

• Base: 7.9/11.5 (that's 8 turns V 6 turns to kill an orc Warrior)
• CE (Billhook) CEHH (Javelin): 7.6/10 (that's 8 turns V 5 turns to kill an orc Warrior)
• KFCEH: 6.1/7.2 (that's 6 turns V 4 turns to kill an orc Warrior (3.5 to be precise))

And we're not taking injuries into account.

It doesn't depend at all. The Billhook is arguably the best polearm in the game, and under no scenario will it outmatch the javelin damage-wise, since the Javelin will shoot twice per every Billhook swing. I'd like to see a Billhook Vs Throwing Axe against Ancient Dead, though.