The area right by The Howard Theatre has really done downhill in the past year or so.

You'll get plenty of young professional tenants easily in both places, so the decision really only comes down to the trajectory of future expected rents vs the price. U Street has a more stable rental market, but the properties are more expensive. That end of U street is also projected to have a lot of new construction on old Howard properties, which means more (and newer) competition for your rental, whereas Columbia Heights is mostly built out. If you're well diversified and therefore more able to manage some risk, then Columbia Heights is probably the better move, but the difference isn't large. Whatever quality of life differences there are between the two are mostly already priced in.

I'm sorry for not giving a context. Which one is a better place to buy rental properties?

OP you need to share a bit more context than just “is this place good/bad”?

Are you a 22 year old single personal trainer at a gym nearby looking for a one year apartment lease, or are you a family of 4 looking for a row house to live in and a safe neighborhood for the next 30 years?

Is it similar to Columbia Heights or worse?