4lb fire line..
I totally agree.
Braid is indestructable and is extreamely small in diameter, but it also doesn't stretch.
The no stretch allows to detect even the lightest of bites no matter how deep you need to fish.
And I like 4# over 2# incase something larger wants to hit.
Like a large bass, walleye, or even a steelhead.............................which happens often for us.
I don't feel you gain much using 2# over 4#. With braid anyway.