There are more than two ways to go to Hanoi from Ho Chi Minh or the opposite direction but if you want to stay in Vietnam there are two main options. One is Hanoi road and another one going through Ho Chi Minh road. They are both good, concrete roads, you will not be disappointed with both of them.
Hanoi road is going next to the coastline, it’s definitely more busy than HCM road. All of the buses and lorries are going there so is you want some peace on the way – don’t go there. The road mostly looks like a highway, there are plenty of petrol stations. For me it’s a bit boring though, the same view all the time and in fact mostly nothing special.
Ho Chi Minh road is definitely more quiet way. There is no many people on the way – specially tourist. Beautiful mountain road which starts around 500km away from HCM and goes all the way to Hanoi. There is no problem to find a petrol station or mechanic. Exception is when you go through national park – obviously. There are only few houses for 50 km, no cars, no people. If your motorbike will breake there… Better no.
For me HCM road is a way better. Good concrete path is anywhere you go but you will not have so much dust from cars and people going on your way like on Hanoi road. There is not much hotels on the way but you will always manage to find a place to stay for a night. If you want something more than to go as fast as you can from one side of Vietnam to another one then I can highly recommend it to you.