Frenzy is SLOWER than bash for fury generation, even with the increased IAS.

Reason 1: Frenzy is only 3 fury gained each hit. Bash is 8 fury gained each, and it becomes 12 fury with instigation (4x more than Frenzy)

Reason 2: proc coefficient : Bash has a 1.0 proc coefficient. No randomness, each time you hit you get full fury. Also each time you crit you get Into the Fray proc.

Frenzy has a 0.750 proc coefficient : 25% of Frenzy hits won't generate fury at all, and 25% of frenzy crits won't proc into the fray.

proc coefficient has nothing to do with generating fury per hit as far as i know, but for into the fray procs yes it matters

I have found frenzy to be all around better, and if you are using it properly you will always have 5 stacks during a fight so the 75% ias really helps getting more crits = more fury

but it really comes down to playstyle, if you just want to use it for a quick way to get wwing again then bash is better

but top barbs dont even need a fury generator like bash/frenzy