We will be visiting Laos for a week (in late-February) before a week in Northern Vietnam. We are visiting friends in Vientiane and are debating how to spend the rest of the trip. In particular, is it worth splitting our non-Vientiane time between Luang Prabang and Vang Vieng? (Either 2 nights in each or 3 nights in LP and 1 in VV)? Or is 4 nights in LP alone a better option? A lot of the discussion I've found online is from pre-train days, which seems to alter the calculus significantly.