I recently travelled to Vietnam for the first time last year (2019). Flew direct to HCM and stayed there for just a couple of nights. I heard negative reports from colleagues about HCM before this, which is why I deliberately limited my stay there. Turned out to be a good decision.
HCM is a city still in transition. The town center is one large construction site, and who wants to spend their holiday in a construction site? There's not much public transport available, and the streets are choked with motorcycles. During rush hour they even clamber on to the sidewalk. As a result, you're in constant fear for your life as you try to avoid the seemingly oblivious hordes of motorcyclists. There's also not a whole lot to see. Wasn't too impressed with the markets, and wasn't too interested to make the trip out to see the war tunnels. So much for the negative aspects of HCM. On the plus side, I found a really beautiful Scandinavian style hotel converted from an old bank building. I also liked the old streets with French style townhouses and grand old tropical trees. Food was good.
So much for HCM. Then we flew up to Dalat, and it completely redeemed the trip. Gorgeous highlands with flowers all around and mountain lakes. Fantastic coffee culture and French-Vietnamese fusion cuisine. Stayed in a slightly creepy but beautiful art deco French colonial retreat. Very nice weather.
On the way back, my wife got verbally attacked at HCM airport by a communist era airport guard. She got mad and vowed never to come back. But I would totally totally return, but only to Dalat.
Dalat - mountain lake at sunset
Dalat - Ana Mandara resort
Dalat - delicious stinky fermented meat rolls