Which version sounds better depends on who's reading it. "Iota" is itself used to mean something small or insignificant ("it wouldn't make an iota of difference") and I couldn't tell you where it is in the alphabet - I can recite "alpha, beta, gamma, delta, epsilon" but can't get beyond that.

On the other hand, "beta wolf" is clearly a play on the existing term "alpha wolf" - it would probably be better if they actually used that for the top ranking title rather than "leader of the pack", but the meaning is the same. (Perhaps they started as matching titles, then someone said "hey, let's call the top one 'leader of the pack' instead" and didn't change the other for whatever reason.)