The lowest rate I’ve seen on the Hilton website was around THB 6,750++ for the WA.
The next BTS station is few minutes away. A few stations to the river, where you can take a boat to some top attractions. Most shopping centers are a few stations away or in walking distance.
Personally I don’t like the MH. From my point of view, the MH is a 4 star tourist hotel and the WA is a 5+ star luxury hotel. If you know luxury hotels (like the WA Amsterdam), the MH will disappoint you.
I think, the WA is the right choice for you.
Don’t forget your registration for the Go more, get more promotion with double points from the second stay on.