Ah, another reason for MD...
You can not be admitted to the MD bar on motion, so it makes sense to take the MD bar rather than the VA bar.
http://www.ncbex.org/fileadmin/mediafiles/downloads/Comp_Guide/2007CompGuide.pdf
That makes no sense unless you want to be in MD in the first place. Florida allows no waive-in, but I would be crazy to take the Florida bar if I lived in DC
It's not about wanting to be in MD. It's about keeping your options open with as little hassle as possible.
If you take the MD bar, you can practice in MD and DC. After 5 years you can waive-in to VA and practice in MD, VA, and DC.
If you take the VA bar, you can practice in VA and DC. After 5 years you can practice in VA and DC.
Re: Florida... If you have no connections to Florida and never plan to practice there, then yes, you would be crazy. If you went to school in Florida or have connections to Florida, it's not crazy. Plenty of attorneys in DC took the bar in the state that their school was located in and then came to DC. A lot of people come to DC for less than 10 years and then relocate back to their home state.
The following is of course is second hand info, but I spoke with an attorney I know who took the MD bar (and practices in DC), and he said it's because MD does not require CLE (and VA has restrictive rules about what qualifies as CLE), the MD bar has fewer subjects and is "not quite as stuck in the 17th century as is VA state law," and the waive-in provision I mentioned earlier (better to be able to practice in 3 states after 5 years if you want to, rather than just 2 states).