I agree that LACs provide terrific preparation for law school, but I’m not sure I agree that they’re necessarily better than universities, small or large.
It really depends on the colleges in question, one’s intended major, and how selective one is about choosing courses. Certainly someone majoring in, say, math or classics* is unlikely to run into large classes even at the largest universities, not to mention classes in the relatively unpopular, specialized departments that universities have (e.g. Scandinavian studies and geophysics). I can count the number of 20+ student classes I took in college on one hand (specifically, organic chemistry I/II, ecology & evolution, and genetics), with the others having 10-15 or even fewer students.
That said, economics is an extremely popular major these days, though it’s fading in popularity relative to computer science, and it’s more prone to lectures than seminars. Economics classes will be large at many colleges…it would be prudent to glance over course schedules at a college of interest to get an idea of how large classes are.
*Incidentally, classics majors fare the best on the LSAT, followed by math and philosophy majors. All three subjects involve small, highly analytical classes.
On an entirely different note, some universities allow advanced undergraduates to register for law school courses with permission (e.g. Stanford, Duke, Penn). Even where cross-registration isn’t allowed, many professors would welcome a curious undergraduate to sit in on a class. The opportunity to taste law school life (or, indeed, grad school life in general) is not an option at many LACs. I wouldn’t put too much weight on this, but it’s perhaps something to consider.