Wow, that is an obnoxiously long title. I meant to compare these two polishes ages ago, but...well, I've compared them now so here we go.
Color Club Ready to Royal and OPI William Tell Me About OPI.
Ready to Royal is definitely a darker color that leans more towards black. William Tell Me About OPI is more wine-colored. As far as formulas go, they were pretty much equal, and although you can't beat OPI's Prowide brush, it really just depends on which shade you prefer. And then, just for fun...
Color Club Catwalk Queen and Groove Thang are shimmers, I compared them next to Ready to Royal and William Tell Me About OPI. Catwalk Queen is redder than all the others, and Groove Thang is more blue. From darkest to lightest, they'd be: Ready to Royal, Groove Thang, William Tell Me About OPI, and Catwalk Queen.
These vampy colors were popular this fall, so plenty of brands came out with their own versions. Groove Thang and Catwalk Queen are from fall 2009.