Anything properly serious or worrisome, especially regarding a child, then I would consider going to BBK.
Horses for course though.
The hospitals in Korat are OK for many things but I'm sure everyone who has lived here for a while has heard disconcerting stories about the services here at most of them. Maharat is a university instructing hospital that's packed-out by Thais, St. Mary's is hit-and-miss (good dentist though), Korat Memorial is a cosmetic alteration hospital for women really that pretends to offer other services, BBK Hospital in Korat is OK if it's not a serious condition and you don't mind spending lots of money as it masquerades as a 5 star hotel with nurses instead of waitresses, and the one at or near SUT I can't comment on.......might be OK as others have said but would probably depend on how serious your case was, especially if the hospital isn't finished.
Nothing guaranteed at any of them here in Korat, I reckon.
It is true, as mentioned already, that many of the doctors here work at different hospitals in Korat at certain times and there's a good chance of being seen by the same doctor at different hospitals.