Let's see, several million less dead and maimed in SE Asia vs OTL?
Far less ecological damage from defoliants and no 100's of kilotons of hazardous UXO scattered from all the iron we dropped on the Plain of Jars and other spots during the bombing campaigns?
The USA doesn't face-plant itself to the tune of 60,000 dead and 300,000+ disabled veterans and ~200 billion dollars (in 1970 dollars)?
If played well, American companies get access to Vietnam and we get bases at Cam Ranh and Da Nang anyway?
I don't pretend the North Vietnamese were saints by any stretch. Plenty of GIs captured by the NVA were tortured and abused in captivity. They weren't any nicer to political opponents when they took over, but compared to the Khmer Rouge, they were models of sanity and restraint.
However, IMO, this'd have been a lot better than OTL.