Neither actually sounds like a good fit, to me, but maybe I don't understand your definition of "site". Are you talking about something like Weebly, Blogger, Wikia, what?<p>The sub-domains stuff is actually pretty hard in every CMS I've ever used, so I suspect it's a challenge in Drupal, too. Besides that, I don't know that a community-style CMS like Drupal brings you any benefits, does it? By this, I mean, are users connecting in some way? It seems like you're just looking for a way to make scaling out to multiple machines a nightmare. RoR, also, is a CRUD building tool. It's really good for building CRUD apps. I'm not sure what you're building is a CRUD app...but, then, I don't know what you're building.<p>If you're thinking straight up, "build a website" in the Weebly, Synthasite vein, then you probably don't want a framework or CMS at all, except perhaps for the management layer (which doesn't have to scale much at all). Perhaps relevant: I helped a free website hosting operation scale up several years ago, and he achieved his 1.5 million websites scale from a handful of off-the-shelf machines (in 2001, or so) by deploying to static pages. He also could add new machines and re-hash without any trouble at all--no database was involved, except for the creation and management of pages. I believe Weebly does the same (and they're kicking ass with nearly a million websites now, and scaling up without even having to think hard about it, because they designed it appropriately for scaling).<p>I think maybe you need to spend a bit more time thinking through your problem domain before deciding what the solution looks like.