Yes, I agree--LM Plaza Athenee is classier.
A subjective comparison:
Pool and Gym: LM--a nice, sunny pool area, bigger than Sheraton Grande Sukhumvit but not as tropical and shady as SGS.
Club Lounge: LM (Wesin is cramped, crowded)
Service: LM
Breakfast Buffet: LM
Location: Westin (connected to a SkyTrain station, also across from SGS, where I think you can still have signing privileges at restaurants, etc)
Room: No winner

As for the gay thing, I don't think either has any issues for or against them. That said, I think either one is going to probably allow you an evening visitor unless it's totally obvious he's a hooker. The larger hotels seem to not want to embarrass their guests by asking, though YMMV.
As for MegaTopLover's comment that there are three hotels with a gay following, he DID do a good job highlighting the three high-end hotels. Here I am to now offer the low end.
Top-of-the-low-end: Tarntawan Place. Decent, slightly shabby rooms, walking distance to all the gay bars, discos, and boy bars. Everything is included in the $80 or so price: tax, breakfast (offered 24 hours, even if you get up at 5pm!), local calls, internet, etc. Room service is good and cheap; even laundry isn't too expensive. Nice choice for a short stay. Less gay than 10 years ago, but still 50-75% gay guests at most times.
Medium-low-end: Pinnacle Hotel Lumpinee. Located about a 3-minute walk to Lumpinee subway station, only one stop from Silom. $50 for their best room through discount booking agents, includes breakfast. Tiny rooftop pool, and tinier gym, where some of the equipment works. Near good restaurants, and also a 10-minute walk to Babylon, if you like that kinda thing. Westerners and Asians from nearby countries in their 20s, 30s, 40s are commonly found here. Probably 50% gay on many nights I've been there.
Low-Low-end: Malaysia Hotel. Hookers hanging out in the lobby. Said to have a good restaurant, friendly service, and a decent pool. Older crowd. Have never stayed there but heard decent things about it surprisingly.