China vs Vietnam

China's $1,100/mo monthly cost (across 5 scored cities); Vietnam's $997/mo monthly cost (across 2 scored cities) — not enough data to call a winner.

China's 3.3/5 safety score (across 5 scored cities); Vietnam's 1.5/5 safety score (across 2 scored cities) — not enough data to call a winner.

China's 3.3/5 mobility score (across 5 scored cities); Vietnam's 2.0/5 mobility score (across 2 scored cities) — not enough data to call a winner.

China's 3.5/5 culture score (across 5 scored cities); Vietnam's 3.2/5 culture score (across 2 scored cities) — not enough data to call a winner.

China's passport reaches 52 destinations visa-free to Vietnam's 23 — China opens more doors without a visa. Passport strength shifts over years of naturalisation, not months of planning, so it's a long-horizon footnote — not scored in the tally.

China is better connected: 755M passengers/yr against Vietnam's 117M passengers/yr. China is busier than 85 of 87 countries worldwide; Vietnam is busier than 68 of 87 countries worldwide. China sees ~53 air passengers per 100 residents a year; Vietnam sees ~1 air passenger per resident a year — a derived figure, not itself ranked.

China runs -10°C to 37°C for most people; Vietnam runs 19°C to 39°C for most people. Harbin runs colder, at -34°C; Móng Cái runs colder, at 1°C. Depends on you — which range fits your tolerance is the real question here, not a score.