The Yor get +25 miniaturization as a racial ability. This is very powerful, especially on large/gigantic galaxies. You can design a +5 speed colony ship based solely on the starting techs. This really helps with the opening planet grab. (You get your new colonies that many turns sooner, which means you get their extra abilities that much earlier, and all that compound interest works heavily in your favor.) I don't know if the AI exploits the Yor ability in this way. It's a fool if it doesn't.