I'd go for the older more experienced staffer almost every time. In Thailand - as most other countries - the young'uns rely more on scans and other equipment rather than past experiences to help in the diagnosis. So already your costs are higher.This is probably not a widely held view, but I prefer to have older, more experienced staff.
And generally here very few Thai doctors will admit they are unsure and will not call for advice or a second opinion until the patient has already run up a significant bill. Then they may suggest calling in another doctor or suggesting, in the case of the Dusit Group, you go to Bangkok for further care.
But I've learned to stay away from the senior doctors, the "professors", those who are in virtual retirement. Care may not be as good, and none of the younger doctors will care to help you out.
One tip - if it's suggested you need to go to Bangkok for tests that the local doctor could not read definitively, suggest instead that they send the digital images to Bangkok, not the patient. That's one of the reasons for electronic medical imaging after all.