I like to stay on Sukhumvit actually as the BTS is so convenient from just about all properties. I really like the LM, however only downside IMO is the location isn't accessible easily to BTS and thus takes some time to get to. The W has a nice hard product, but given it's location and price premium usually I would stay the the LM if I wasn't going to be on Sukh.

The St. Regis definitely has the best hard product of the bunch, but you are paying at least 50% -100% more for probably only a relatively small - medium sized incremental improvement in the overall experience. BKK has so many great properties, I have checked out the JW Marriott and the new Mariott Marquis which will be nice options for some especially after the merge. JW alittle tired, but nice and location better than the Marquis which has a great hard product, but location not ideal with a long walk to Sukh.