Traveling to SaPa from Hanoi on the night bus is an experience that I won’t forget. The seats were almost like beds and double storey. I was on the top level with no seatbelt and almost fell out of my seat more than once!
Try to be one of the first in the queue as choosing the right seat is very important. You don’t want to be on the bottom up the front as the drivers will often tell you to move to let their friends jump aboard. So don’t be surprised when you go through the back streets to accommodate where they need to go! So if you like the front choose the top level so you don’t get booted from your seat. Also try to avoid being to close to the toilet as after a few hours it may start to stink the bus out.
Going there I was on the top and had a fairly good experience coming back I was on the bottom and much preferred the top. Especially being a solo traveller I felt much safer from thieving hands and just the general public. Keep all your valuables on you- your passport, cash, cameras the lot! They will go through your bags and I heard people on my bus who lost stuff, I also heard people getting underneath the bus to go through the bags…
I have also been on a night train in Vietnam and honestly greatly preferred the bus! Comfortable seats, controllable aircon and wifi as well as cheaper tickets are all a big plus in my opinion compared to the train! The main thing is if you are tall you may be a bit squished but it will be an experience you probably won’t forget!