We had originally booked seats on a minivan from Vang Vieng to Vientiane. We got picked up from our accommodation and dropped at the bus station where we changed our minds. We prefer not to have our bags loaded onto a minivan's roof. What if it rains? They usually make some effort to cover the bags but I don't trust it. At least on a big bus you can hold your bags between your legs like in the photo above or put them in the bus' storage compartment. Yes, that is my finger in the photo. Plus the minivan was already so full that people were sitting in the aisle. We were in no rush so we decided to wait for the next one. After some back and forth we got our ticket transferred to the next bus.
The distance between Vang Vieng and Vientiane is around 150 kilometres on a winding pot holed dirt and some bitumen road. It is not the most comfortable road. I doubt it would be comfortable even in a fancy 4WD. Maybe a little more fun though.
All the signs in Vang Vieng say that it takes around three hours to reach Vientiane. Unfortunately, this is probably a little optimistic and you are probably looking at something more like 4 to 5 hours. The time all depends on the weather conditions and the amount of traffic trying to negotiate their way around the pot holes and each other. The time also varies depending on how fast your driver wants to drive. The slower the better to be honest.
The cost of a ticket for a big bus from Vang Vieng to Vientiane is between 45,000 Kip and 80,000 Kip depending on what time you want to leave and where you purchase the ticket. We purchased ours for 60,000 Kip each from Phongsavanh Bungalows where we were staying.
Mini van or mini bus tickets typically cost around 60,000 Kip each. They also leave at different times of the day. You'll need to ask around to get a specific time as minivans schedules are often highly variable depending on demand.
About half way through the journey, the bus / van stops for a short break at a road side shop and restaurant. The toilets are clean and cost a couple of thousand kip to use. They sold chips / crisps, icecreams and made fresh baguettes.
All in all, we find travelling on a big bus much more comfortable than travelling long distances in a minivan or a minibus. Of course, if we could get one whole seat each on a minibus or a minivan, then it may be a different story.