I had a quick look at this myself and did some basic math.
This is about the difference between careful attack and twin strike.
Where
x=basic damage for the weapon
a=the chance to hit
HQ=hunter quarry
I have assumed that both the main and off hand weapon are the same with the same enchantment bonuses
For Twin strike you do:
a(x+HQ)+ax=ax+aHQ+ax=2ax+aHQ
For precise strike you do (assuming a d20 to hit
)
(a+2/20)x+(a+2/20)HQ=ax+0,1x+aHQ+0,1HQ
So if we balance these to to find out at what to hit they give the same benefit.
2ax+aHQ==ax+aHQ+0,1x+0,1HQ
ax==0,1x+0,1HQ
Say (to make this really easy) that both the swords are longswords and everything has the same enchantment bonus and that we have the lethal hunter feat that make HQ d8's.
a==0,2 which means that is you hit on 17-20 they give the same benefit, if our to hit is worse we should use careful attack and otherwise twin strike.
If you find anything wrong please tell me
The thing about this little exercise is that this favors twin strike quite a bit. Both the weapons have a the same enchantment bonus and both weapons are longswords instead of having one offhand weapon.
And about the issue of reaping strike vs sure strike the thing is that that is not even a contest. Not because sure strike is so bad but because reaping strike is so fantastically good.