Hi!
I had this same question, since I live in DC currently and Maryland is obviously the closer choice. But I really wanted to do an online program as it would allow me more flexibility between my career and personal life.
However, I spent a lot of time looking into each schools research programs, the bios of each professor, where alumni ended up, and then determined based off that which school aligned with my educational and career goals the most. At the end of the day, you will be qualified to be a social worker from either school and both programs are excellent, but try to read up on the professors and determine which ones you would like to study under the most. You can also look up professor ratings and reviews from students on sites like RateMyProfessors. If you would like to stay in the DMV area and try for a high-pay government social work position, I don't think you can go wrong with either as u-maryland has connections in DC, but so does Columbia and it has that known Ivy League name. If you want to try eventually for a leadership position in any location, you might get more of a foot in the door by having the Columbia name in your resume. Butttt, if you are just a really good social worker and get good references and recognitions from the places you work, you can obviously still have opportunities to land high level positions regardless of the school you went to.
I hope you are able to figure out your perfect match!