Large servers struggle to make the appearance seem personal. Mainly because they cost more to run for the hardware and bandwidth required. With this comes a bigger push on players to spend and vote. There are still those who do it for the passion of it, but they are far and few between. The best largest server I ever played on, with a nice community was Vox Populi.
It is difficult for new / small servers to provide enough variety in a world that is saturated with servers and experienced players. Even seasoned veterans have fallen foul of it (e.g. Favorlock with his Nyxcraft network. A prison server with custom plugins, highly polished, well advertised, large and competent moderator team, yet failed to pull in the numbers required).
With smaller to medium sized servers, it is fine if you already have an established brand name, some experience and an audience to draw from.
Smaller servers tend to survive better when you add more of a personal experience to it. I've had many memorable experiences over the years on small / medium SMP/Bukkit/Spigot/Tekkit/Direwolf servers than large ones.
So, big, or small? I prefer medium sized, as you get the best of both
