Other Car Rental Programs/Partners (ie. Alamo, Enterprise, Sixt) - Help me decide, DCA or Union Station?

I need to rent a car in D.C from Jul22-Jul26
DCA rates are $240.72
Union Station rates are $156.42
There are different vehicles involved but the bottom line for me is saving money!
How difficult is to get to Union Station from DCA?
Do you know of any valid discount coupons?
Thanks for your help.

P.S. I am not familiar with D.C. are, but I can manage to find my way around places.

Union station is very close from DCA. In fact, it has its own metro station. you should get there probably within 20-25 minutes from DCA through Metro. I never knew it could be so much cheaper to rent from Union station than from DCA!

FYI with Alamo/National, you can pick up at Union Station and drop off at DCA for no additional charge.

Szymon

Catch the metro from DCA to Union Station.

Be careful, there are two different lines that service DCA. Both will require one transfer to get to Union Station, but at different stations.

This map may help: http://www.wmata.com/metrorail/systemmap.cfm

Catch the metro from DCA to Union Station.

Be careful, there are two different lines that service DCA. Both will require one transfer to get to Union Station, but at different stations.

This map may help: http://www.wmata.com/metrorail/systemmap.cfm

The fastest way is to take the Yellow Line to Gallery Place and go upstairs and take the Red Line to Union Station. It's very easy to get there.

The Blue Line is slightly slower but if you arrive during non-peak hours it would be quicker to take the Blue Line rather than waiting 10 minutes for the yellow line.

Thank you for all your input! I successfully completed the transaction, taking into account all the tips above!!