A blue die has an average damage of .75
so you can say "on average" to spend a blue die to activate LS you will be sacrificing .75 average damage (effective damage is harder to calculate and can be situational, eg braces etc)
25% of the time you will be sacrificing an accuracy on a blue and 75% of the time you will be sacrificing a hit or crit
Both LS and OE are going to reroll whatever black dice you need to re-roll so thats a wash
LS will re-roll the OTHER blue die and the red dice as well (on average) so what what you are really looking at is -.75 damage (on average) to pay for an on-average increase of X. Since it is a selective re-roll it is much more powerful than a complete re-roll in that (for example) you can pick out your blanks and extra accuracies and now will increase your average damage potential for the total dice pool by X - .75