Two rangers in the same fight... one with First Reaction, one with Lethal Hunter, both with 1 action point. They both get surprised by a group of hobgoblins in a 6 round combat.
Surprise Round:
A (First Reaction) Spends an action point to act in the surprise round. Nimble Strikes a Hobgoblin Soldier for 1d10+4 (35% chance to hit, 3.325 avg damage).
Round 1-6:
A (First Reaction) Marks a hobgoblin and careful strikes for 1d10+1d6 damage. (4.95 average damage)
B (Lethal Hunter) Marks a hobogblin and careful strikes for 1d10+1d8 damage. He then spends an action point and takes another careful strike (either 1d10 or 1d10+1d8, depending on whether he hit already with the quarry. Technically, he could only use the action point if he misses to maximize its damage) (5.5 avg damage normally, 8.525 avg damage in round with action point - add another 2.025 if you guarantee quarry applies)
So in this surprise combat...
A (First Reaction) - 33.025 avg damage, 7 standard actions, 6 move actions, 6 minor actions, 1 action point spent
B (Lethal Hunter) - 36.025 avg damage, 7 standard actions, 6 move actions, 6 minor actions, 1 action point spent
And, hey, in any combat in which there's no surprise round, B totally wins. Just like the combats with surprise rounds. But more.