I recently ran Kosher Kush, Holy Grail Kush, Kandy Kush, Skywalker Kush, OG18, Sour Kush and RP's OG Kush for comparison, all in the same organic soil, medium fertility. They gave me no nute or PH troubles at any stage. They are all sensitive to light leaks and will herm on you at 2-3 weeks in the lower bud sites. The few I saw I just plucked them off when I was cleaning out the underbrush. (Very slight light leaks due to flip flop.)
The Kosher and Holy looked very similar, both with dense round buds. The HGK stank more but neither had very impressive frosting. That said, this weed would be considered awesome by most smokers I know. The HGK was a low yielder and brittle, it kept tearing itself apart around week 7. Most of the time I am too lazy to stake them or tie them up.
The Skywalker was very dank, icy, dense, potent and popular but also brittle.
The O18 was awesome, very dense, very OG stanky potent icy buds.
The RP OG was the slowest (~9.5 weeks?) unimpressive yield. The dankness and potency was there. The flavor was top notch chemmy OG.
The Sour Kush was awesome in every way except yield. It was the strongest dank smelling and it had staying power in the jar. Nice hard icy nugs with massive fuel. Brittle branches.
And finally the Kandy Kush. This was the keeper for me. Decent yield, tons of frosting, very strong OG funk with fuel and a slight bit of cheese. True the nugs were not as hard as the O18 but they weren't fluffy by any means either.