SGN-HKG timing question

[pilot]

I'm looking to book SGN-HKG oneway in early January. Apart from UA at an unearthly hour, there appear to be 3 CX/VN direct flights. However, departure and arrival times of these flights are subtlely different between CX and VN.

VN 762 SGN 10:05 HKG 13:45
CX1762 SGN 10:10 HKG 13:45
VN1766 SGN 11:25 HKG 15:10
CX 766 SGN 11:40 HKG 15:20
VN1764 SGN 18:55 HKG 22:35
CX 764 SGN 19:05 HKG 22:45

Not a big deal but is there any explanation? I'm just curious.

Also I know it's a short flight but is there any recommendation between the two daytime flights?