People say overpower is more enmity if you include Unchained.
Unchained -> Overpower = 120 * 5 = 600
Steel Cyclone = 200 * 3 = 600
So for the first GCD they will have equivalent enmity, but starting from the second overpower.
Unchained -> Overpower -> Overpower = 1200
Steel Cyclone -> Overpower = 600 + 450 = 1050
You can obviously Steel Cyclone -> Infuriate -> Steel Cyclone = 1200 but you will fall behind on the third GCD.
Unchained has a 120 second CD so you can't do this all the time, and honestly either way will hold aggro on anything but if you absolutely need to maximize enmity, unchained -> overpower is the way to go.
edit: it is worth noting you do not need to target anything for steel cyclone which might let you start building enmity much earlier and has the ability to target mobs behind you.
