If you guys think about it, in a standard 10 turn battle (20 turns over 2 monsters w/o healing) the Blue is probably a better choice.
Mathematically speaking, with LS at 20% with blue, you should get at least 2 LS in a 10 turn battle. Since they are halved in damage, the damage should remain the same.
However, your LS drops to 5% with red. Meaning you might not even get it in a 10 turn battle. So say throughout the entire 1st 10 turn battle wearing the red cap you get no LS, but in the 2nd battle you finally get a LS that's doubled in damage; however, the monster is probably close to dead or dying anyways. Again, mathematically speaking, there is a 50% chance (per battle) of getting 1 LS from the Red Cap in a standard 10 turn battle.
To me I'd think the Blue is much more useful (especially now since there are short battles, some lasting <5 turns). I'd rather have 2-3 LS per battle even if they were marshmallowed than have 1 LS every 2-3 battles that would probably overkill the monster. Though I can see the Red Cap as being a for-fun thing, like reaching the 7000 damage cap with even harder circumstances (damage cap on GoldenZard? etc...) Or with a few exceptions, such as Sin Qua Non (3)...