After staying at these properties, I can provide my opinion.
3 nights at the W Washington Hotel were exceptional. As mentioned above, I did not use any SNAs so they only provided me an upgrade to a Spectacular Room. I wasn't bothered since the SPG website didn't show any suites as being available that day. The room was small, but modern and well kept. The view was also nice with the Treasury Building providing a soothing orange glow in the evening
While most choose this hotel for the convenient location, I will be coming back for the phenomenal service. My entire stay, the service was proactive, engaging, and genuinely helpful. From ordering room service off the the in house restaurant menu, to personally escorting me into the rooftop lounge, they raised the bar in terms of service I have experienced at a W property. Unless you are completely put off by W styling, or are traveling as a larger group without a suite, I would highly recommend this DC property.
1 night at the Pentagon City Sheraton was, on the other hand, average. Dated property, but the room was large, clean, and had high ceilings. The hotel also provided me a room on the club level with very nice views of the Pentagon and Air Force Memorial. Being that the hotel was completely booked, the room was not treated as an upgrade, so I appreciated that they provided me a high club level room. The club lounge itself was also convenient for a quick bite or drink. A word of advice for those intending on visiting Arlington Cemetery while staying here. The hotel is close to the back entrance of the cemetery, but that apparently requires military identification to enter, The main public entrance is on the complete other side of the cemetery, requiring a 10min drive. All in all the hotel didn't exceed my expectations, but didn't disappoint either, which is a win in my book for a US low price Sheraton.