It won't make too much of a difference in accuracy for any long range shooting, but anything closer then 5 meters will be easier to shoot. Mainly you will notice it breaking significantly less but that is about it.
In siege most of your shots will be close enough that it might be worth it simply for the saving in cash.
I thought all breaking was based on your highest WPF, regardless of which kind it was? So, his xbow break chance would be based on his 1h wpf... isn't that what it says in the mechanics thread?
Edit: Tracked it down, I was wrong. " For melee weapons highest melee skill is chosen, so for example using a long spear with 1 polearm wpf while having 120 wpf in two handed uses the 120 wpf for breaking. For ranged this kind of mechanic isn't in effect, and bow breaking chance in determined by archery wpf etc." Furthermore it looks like that thread is referencing your research, ToD, so I should never have doubted you
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