I usually have one or two single bevel and one or two double bevel broad heads in my quiver at the same time. And have for a number of years. Which one I pull out to kill a critter is a matter of chance.
I've shot two-and 4-blade Zeikey deltas for a lot of years, and they are excellent heads, but unfortunately, that design does not make for a good single bevel construction. The front of the head is triple laminated, which makes it strong but it also means that 1/3 of the head is not part of the single bevel. In fact, it's working against the single bevel. Also, when you get past the triple thickness point, the thickness of the single blade remaining is rather thin so a single bevel there has very little effect on the broad head's ability to turn in a critter.
I really like Zwickey heads and it pains me to say this, but if you want to shoot a single bevel, there are better choices out there -- Abowyer, Grizzly, etc.
Regardless, regarding penetration, I've found higher FOC and skinnier carbon arrows shaft diameters have a much greater effect on penetration than broad head blade bevel.