He didn't ask which is easiest. He asked which is the most efficient and gear independent. There are a lot of varying opinions on this, but in my opinion, Blood is neither of these. I say Frost is stronger than both Blood and Unholy when your gear is weak, and is competitive with Blood at average gear. It loses traction when you're near BIS, especially if you're building armor because Unbreakable Armor will put you over the armor cap - thus diminishing its usefulness.
As for efficiency, it depends on what sort of efficiency we're talking about. Are we talking about raid efficiency? Blood has terrible multi-target threat, and in a 10-man raid setting, the only thing it likely provides for the group is Hysteria. An Unholy/Frost hybrid tank that specs into Imp. Icy Talons and Ebon Plaguebringer is more efficient in all of this.
Or perhaps we're talking about surviving efficiency? Both Frost and Unholy have CDs (Unbreakable Armor and Bone Shield) that are perfect for dealing with the melee portion of Soul Reaper, while Blood has slightly superior healing to Unholy. Death Strike heals for the same, leaving only Rune Tap, Vampiric Blood and Blood worms-which nobody takes on here.
I mean, I'm pretty sure this dead horse has been beaten a million times already, but I also want to make sure the guy knows specifics that he asked for. Ultimately, there are 50 thousand different opinions on what is better than what, and I often choose to settle for "agreeing to disagree". But the point is that there is no universally "best tank spec".
I would agree with that. Blood is not a bad starting point for beginner tanks due to the small learning curve.