Give blue to the least efficient person on your team (IE Non Mana using/low CDs) that never dies, or blue to the extremely mana dependent caster on your team with high cooldowns, but always dies almost instantly to the other teams caster?
Generally you want to give buffs over to the person who is going to make the most impact in the game with them. Most people give blue to casters and mages because it helps them do more for your team than you, as a jungler, may be able to do with a blue buff (ie. it's more useful on them than it is on you). Likewise, red buff is typically given to AD carries because they have the range and AA to get the most use out of it.
As for your situation, you can also just take it for yourself. Blue buff isn't going to do much good on a caster who gives it up immediately. At the same time, if you give it to someone who doesn't die, but doesn't really do anything for your team, it isn't going to do you much good either. It's about maximizing impact with the resources you have.
Alternatively, Blue buff can be pretty useful on AD carries, especially Ezreal/Corki, and can also be good on manaless champions like Zed and Riven.
If the mana dependent caster is not able to utilize the blue buff properly, there is no point in giving it to them. It is more worth it to either:
Give it to someone who could use the CDR
Give it to someone who could use the experience (I typically take it for experience if the mana dependent champion can't utilize it).
You definitely dont want to waste a buff on someone who is just going to give it up by dying. The experience the buff kill provides is just as essential as the buff itself.
Hope this helps. :)
least efficient person on your team (IE Non Mana using/low CDs) that never dies,
If we're taking it as a premise that your 
is never going to die, he's more than likely going to hard carry the game. Give it to him so he hits the gold necessary for his core items quicker.
