Neither is particularly well located. RC is on a dark side street with not much else there of note. (Compare to the original RC, now the Taj, which is almost perfectly located at the start of Newbury Street and directly across Arlington Street from the Public Garden.) Marriott LW is a bit of a hike to any of the "sites."

You'll find several Marriott family properties with the word "Copley" in their names. Any of those will be well located for walking. Within a fairly short walk of these hotels you'll find upscale indoor malls (Prudential Center, Copley Place, and these two large malls are connected by an indoor, heated walkway over Huntington Avenue, which runs between them), trendy, boutiquey street shopping (Newbury Street), lots of restaurant choices, some interesting things to see (Boston Public Library, Skywalk Observatory at the John Hancock Tower, the Maparium at the Mary Baker Eddy Library at the Christian Science Center).

The Marriott Copley Place and Westin Copley Place are colocated with the Prudential Center and Copley Place malls, and all four are easily accessible from each other without going outside.