Hunza or Skardu
One week, one valley, and a real decision to make. A straight comparison with a verdict at the end rather than a shrug.
Almost everything written on this question comes from someone who sells trips to both valleys and therefore refuses to choose between them. We'll choose.
They are not variations on a theme
Hunza is narrow and green: terraced villages stacked above the river, with Karimabad as the obvious base. You can get there without a vehicle and you can walk the place once you have. Better infrastructure, longer season, fewer ways for the plan to fall apart.
Skardu is a wide cold-desert bowl on the Indus, sand dunes at altitude with the Karakoram standing behind them. Everything is further from everything else, transport stops being optional, and the season is shorter. It's also where the serious mountains are, and nothing in Hunza answers that.
Getting there is part of the decision
Skardu has the better flight: more traffic, larger aircraft, more services than Gilgit. Hunza has no airport of its own, so you come in through Gilgit's smaller and more weather-exposed one, or you drive.
But Hunza's road stays open year-round and needs no flight to go at all. If your dates are rigid and a cancellation would wreck them, that asymmetry beats the better aircraft every time. We've sat out weather at Skardu airport. It is not a story you want in the middle of a short trip. See Skardu and Gilgit flights.
Choose Hunza if
You have five days or fewer. This is your first trip to Pakistan. You don't have your own transport. You'd like to walk out of your room to dinner. You're travelling outside the June-to-September window, or you're coming for the blossom in April or the gold in October.
Choose Skardu if
You're trekking. Or you want to stand near mountains on a scale that rearranges your sense of proportion. You have a week or more, transport or the budget to hire it, and dates that fall between June and September.
The verdict
Five days or fewer: Hunza, without hesitation. Less of a short trip disappears into logistics, and you can arrive with no vehicle at all and still have a full week. Stay in Karimabad. Where to stay in Hunza explains why, and which of the four villages suits you if Karimabad doesn't.
Ten days or more: do both, in that order, via Gilgit. The 14-day itinerary is built exactly that way.
Trekking: Skardu, and it isn't close. Everything starts there.
Related
Best time to visit Hunza · Best time to visit Skardu · What a trip costs