Great question and I'd like to hear other investors' input on this as well.
My thoughts on renting by room closer to Arlington would be that you could most likely pull a slightly higher rent since any difference would be split between the tenants and not as impactful to them individually. It may be easier to find tenants as well if you're not planning on using a third party.
As for renting to a family in the suburbs, there is obviously a general movement away from the city that could drive demand for those areas long-term. Another perk of renting to families vice single professionals in their 20s (generic Arlington demographic) is that they will generally treat your property better, and are likely to give you much lower turnover rates. Also, you are more likely to get tenants that are open to rent-to-own options if you're looking a little further out from the city. I would definitely look into this strategy if you haven't already! It's one that works well for our area, especially on the properties in A/B suburban neighborhoods.