Does taking a year off, to work as a junior research fellow or as a research intern, immediately after one's undergrad help with admission to a better MS (research track, not professional) /PhD program? If it helps, the field in question is computer science, specifically at the intersection of computer vision and machine learning.
I don't see how it could hurt. The degree of added value most likely depends on what your background is prior to the year as a researcher. If you already have a very strong research background as an undergraduate, an extra year of experience will not help as much as if you have very limited research experience.
I suppose it also depends what you get done during that year. It certainly helped a former student of mine, who didn't get into his desired programs straight out of undergraduate. He took a year to work as an RA in my lab, wrote a first-author PNAS paper, and then was admitted into the top program in his field.
I believe the value of such internships is greater for "marginal" or "borderline" cases, where the overall case for admissions might be weaker than typical because of poor grades or lack of significant research experience. In such cases. having the extra year of experience can help somewhat. I note that, at least for US admission cycles where people apply in the fall semester or trimester for the following fall, such a path may lead to a potential recommendation writer having known the student for only a handful of months—not necessarily enough time to write a full assessment of the applicant's qualities.