You are between Washington and Baltimore, somewhat closer to Washington. Whether an indoor antenna will work for you depends largely on your height with respect to the nearby terrain. You might as well buy the best outdoor antenna for your application, which may be an 8 bay bowtie, since they only cost about $60, and try it indoors first. A preamp might not be needed for Washington reception.
One small advantage of pointing a fixed antenna at Baltimore is that a fixed antenna would also receive the Maryland PBS repeater in Baltimore, whereas an antenna pointed at Washington would have difficulty picking up WMPT from Annapoplis, which carries the same programming. On the other hand, you would be giving up WETA, but until such time as WETA moves its transmitter from Arlington to Washington, you might not get them until then even with a properly aimed antenna.
I think you should use a rotor, regardless of whether your installation is indoors or outdoors.