Impact with respect to what exactly?
For things like graduate school admissions, making decisions about what fields to pursue, or just general experience building, the point is to get *some* research experience. Whether that comes from working with a local research group, an REU, a senior thesis project, or some other means doesn't matter all that much.
For what it's worth, as an undergrad doing work in a group where you're getting a publication is about as good as it gets. If you enjoy the work, are learning from doing it, and there are continuing possibilities for more publications, I'd certainly stick with it. I would only change if you really feel the need to explore other options, have decided you want to go into another area for graduate school, don't like the group, or don't feel like you're learning anything.