As an add on to my Vietnamese trip I am considering a 3 night stay in Siem Reap or HCMC. In terms of 'things to do' it appears that Siem Reap will have more appeal to me but am I missing something in HCMC? My interest in ancient history is probably greater than in modern history, but this isn't the only factor. Which is the better place for food and other interests? As a reference point I'm also staying in Hong Kong and Bangkok on this trip for flights and I know both reasonably well.