I have not stayed in the Springfield VA area before but have stayed at many other Marriott properties in Northern Va. Of the three listed for Springfield I would lean towards the Residence Inn. It ranked higher in reviews on both Marriott's website and Trip Advisor. The Residence Inn has free breakfast and evening socials on select nights. At Courtyard you would earn more points for your stay but breakfast is not included.
If you don't mind a small commute you may also consider the Falls Church Marriott in Fairview Park. It's located about 6 miles from Springfield and as a Gold Member you would have access to their Concierge Lounge. I have stayed at this hotel many times and have always been treated well.
Ok so I'm sorry for the delay butt..........
So far I have been staying at the RI on backlick rd in Springfield. While I have a few quibbles, most of which everyone has, this is a fantastic hotel. Granted I have been there for close to a month but the staff is great, friendly and I really like it.
I had toyed with moving to the CY to maximize the pts but I did stay there once in June and I believe the point differance is to compensate for the amenities difference. The room was smaller, not even a mini fridge, and a few other things.
In summary, If pts are importent to you, or its just 1 or 2 nights, go CY. If comfort is important or wk or longer stays IMO it makes sense to use the RI.
Again if you are there be sure to go to Mike's American grill its just a 2 blk walk from the RI!