This answer is not correct but does show that you are thinking in terms of the stability of the structures that you are drawing. Later in this course, during the discussion of bond energies, we will learn that the carbon-carbon single bond has a bond energy of 346 kJ/mole, the double bond has a bond energy of 602 kJ/mole and the triple bond has a bond energy of 835 kJ/mole. If you add these values up, the two double bonds have an edge by 23 kJ/mole which is not all that significant. It is probably good enough to just count up the total bonds and maximize this number...be sure to take formal charges into consideration while doing this because this is also important.