The bigger king
"Executive King Suite" appears twice in Marriott's gallery for the Belleville property. On extended-stay brands, "executive" usually means a larger footprint and a fuller living set-up than a studio. We cannot give you a square-foot figure, because none is published on the pages we could read. What we can say from the photos is that this is a king suite with more furniture and space than the King Studio.
Who books it
The Executive King makes sense when the stay is long enough that the room becomes an office: a two-week contract, a relocation while you look for a house, or a long medical or family visit in Belleville. Several things help on those stays. There is a full kitchen. The hotel has a guest laundry and a market corner (both in the gallery), and the gym is open 24 hours. It is also a fair choice for a couple who want a little more room on a weekend trip to the County.
What to compare before choosing it
Compare it with the Extended King Suite, which the gallery shows with a separate living area, and with the one-bedroom suites, which add a door. If you need two separate spaces, those may suit you better. If you want one large room with a king bed, the Executive King is the one to ask about.
The casino angle, briefly
If you are here for an evening at Shorelines, any suite works: the walk is the same four minutes. Nothing about the Executive King is designed around the casino, and the hotel and casino are run by different companies. Book it for the space, not for the casino.
Ask about
Ask about the size, the desk set-up, whether the suite has a walk-in shower, and the rate for stays of seven nights or more.