My opinions on the matter.
Black Court Vampires are described as undead; classic Dracula. I wouldn't allow them to be 'cured', because essentially that's resurrection. It also changes the entire tone and feel of the campaign. If a table decides to allow this to be done, it should be very difficult, because if it was easy, it would happen more often. (Hence my comment about making a cure dependent on, say, willing human sacrifices.)
Renfields are so mangled, mentally and spiritually, that they no longer qualify as human. (Which does lead to the interesting question of how damaged a human being has to be to no longer be 'human' under the First Law...) I actually do have a group that can, at considerable cost and risk, sort of recover a person from a Renfield. (As described to a PC, "It's like glueing a Ming Vase back together; it may look much the same, but you can't make the person fully whole again.") It takes a very long time, and since there's also some risk, the group doesn't normally bother. And Renfields are still living beings.
Red Court is much the same as Black Court; they're a type of undead/demon cross, and there's nothing human left to bring back. RCV Infected haven't quite crossed over...but again, if you allow a cure, then you're changing the tone of the universe.
White Court Vampires have all made a choice (consciously or not), so no, they don't get to 'come back'. That would be altering the concept of actions having consequences. They may feel very sorry afterwards that they killed someone; but they killed them. (Now redemption AFTER death is in the hands of Someone Else, and would depend on how the WCV had conducted themselves in life; you might not be able to become human again, but you can chose not to become a monster...) White Court Virgins explicitly can be cured.
Vampire: The Angst...err Masquerade/Requiem is a different game, with a different tone. Even there, a cure was supposed to be very difficult and nigh-legendary; many NPC vampires didn't believe it existed.
For me, it's a question of what type of universe do you wish to play in? What is the tone, the setting? In the basic Dresdenverse, actions have consequences, and Bad Things Happen to Good People. If you start changing that, you're starting to change what attracted us to the universe in the first place.
Again, all the above is my opinion, and should not be taken as a criticism or reflection of anyone's game or setting.