For admissions purposes only, in your case I would strongly recommend a pre-doc (includes RA, e.g. Fed RA positions) over a masters. In general, it seems to me that it is extremely difficult to secure admissions to top programs if you're coming straight from an undergrad institution outside the T50 (or even T20/T10 for that matter), regardless of your academic record or grades. If you're looking for a pre-doc/RA position, you should look for one with economists who have a record of placing past RAs at top programs.