Keep in mind that the research enviromnent at resesarch-oriented PhD-granting universities is usually very different from the research environment at undergraduate-only institutions.
At the larger schools, the main mission of the research projects is to produce publishable results. Many of them do have strong programs for undergraduate involvement in those projects, but teaching undergraduates is still very much a secondary mission. A project is likely to involve some combination of professors, post-docs, graduate students and undergraduates, with the undergraduates being rather small cogs in the machinery.
At the smaller schools, undergraduate education is (or should be) one of the primary missions of the research projects. A project is likely to involve one or two professors and a few undergraduates (no grad students or postdocs because they don't exist at schools like this). The professors should view the research as being an extension of the classroom, and will probably be the same professors that you've had in class. The students will probably take on a bigger share of the work than in a larger project.
At a smaller school, you won't have as big a choice in research projects, and they won't be as "important" in a global sense as at a larger school, but you'll probably be able to get more deeply involved in them, and get experience with more aspects of the research process.