In terms of location, the Sonesta and Marlow are pretty much identical (one's across the street from the other, about a 2-minute walk to 1 Rogers St).

The Sonesta is a larger, nicer hotel than the Marlow, and the Sonesta is on the Charles River. A river view room at the Sonesta would by dynamite: you get a terrific view of Beacon Hill in Boston.

For eating, Davio's in the Sonesta is a better-than-decent choice. The mall (next to the Marlow, across the street from the Sonesta) has the usual chain food places.

The best cheap eats, by far, is at Boca Grande, a taqueria on 1st Street (about a block from either hotel).

If the weather is nice, you can go for a great walk around the river: cross the bridge by the Science Museum, down the Charles River bank, then back across to Cambridge either via the Salt and Pepper bridge (short route) or the Harvard Bridge (Mass Ave) long route), then back down the river bank on the Cambridge side.

If the weather is not so good, the Science Museum (5 mins walk from either hotel) is certainly worth the time. There's also an OmniMax theater in the Sci Mus.