I recommended the Legacy to the OP because, as he mentioned, he can place the speakers close to the rear wall without ill effect. Since the Monitor Audio speaker has a rear port, it is more desirable to have the sealed system on the Legacy. Also the OP mentioned, the Legacy employs a thicker cabinet making it more inert and, given the driver complement, better for bass response. At 110 lbs, the Legacy is significantly more speaker than the 60 lb Monitor Audio.
As was mentioned any speaker will sound different once the OP gets it home and into his unique room with his unique components. However given the size of the room and the placement of the speakers, the Legacy, by design will outperform the Monitor Audio.
Hope everyone had a Merry Christmas!