X or Y rockets?

[Wocky Slush]

whats the difference? which is better? one is more expensive so I assume that one is better

[Joeynator3000]

I haven't played in a while, but I think...X rockets are the big ones that launch from the building, Y rockets are the small ones that split off from the X rocket. So buying more X rockets will give you more Y rockets, and...yeah I think it's best to still buy both.