A difference between the options is how much leverage you get for the premium, relative to the current SP.
Using closing figures, GRKOA are 12.5c/share, and GRK are 19.5c/share. This represents a 15% price premium for the options. This 15% premium buys 156% of the leverage the heads offer.
Similarly, GDYO are 50.5c/share, and GDY are 158c/share. This represents a 26% price premium for the options. This 26% premium buys 312% of the leverage the heads offer.
GRK Price at posting:
0.0¢ Sentiment: LT Buy Disclosure: Held