A dozen students a year is probably too small to have the depth and breadth you'd want to give you a truly "top-notch" CS education (although a focus on theory is far from a bad thing, seeing as how the undergraduate programs even at top-ranked institutions often skimp far too much in that department).

However, all other things being equal, I might vote for the liberal arts school anyways. Smart people are successful pretty much wherever they go, and the most important thing you'll learn in college is how to think. Memorizing Tomasulo's Algorithm or getting really good at handling templates in C++ are relative wastes of time compared to learning how to apply the scientific method and developing general strategies for thinking critically about complex problems. You could do a lot worse as an undergrad than to get a good exposure to the theoretical underpinnings of computer science, study physics and math really, really hard, and spend the rest of your time learning from people who don't spend all day sitting in front of an LCD screen.

The vast majority of the people I've met who have been truly influential in CS didn't get there by mastering their undergraduate material: they made contributions by looking at problems in ways that wouldn't occur to people who only know what's in the textbooks. Additionally, very, very few of these people have been what I'd call hardcore hackers in a traditional, code-oriented sense.

Good luck!