Yes, choose the Sheraton Imperial (or Westin) for better location and more comfortable rooms.

However if you are after a better lounge experience or service, you will be very disappointed. I also do not believe the poster who has made the harsh remarks on LM has actually used the lounge at SI or Westin.

As for Platinum benefits, do note that the LM comp internet in suites (and I presume club rooms) and you have the option of breakfast in the main restaurant. The Westin allow breakfast in the main restaurant but no comp internet in the room, while the SI breakfast is restricted to the lounge and no comp internet in room.