Medical knowledge that enables extremely long life, or the technology that would allow virtual living, will probably have more of an impact on society than the ability to send of a colony ship of any of the discussed designs. Colonizing the stars? Awesome. But the the technology to do so is going to change the way we live on a fundamental level. Population control, wealth, risk assessment, individual drive and knowledge will be different from any society before, the stable outcome is interesting to predict. Using a generation ship or two is a fine platform for exploring those changes, and I think that is more meat for a story than the purely technical side of things - although still important!