The reasons why Vietnamese jackfruit sells better than Hainan may be as follows:

1. Tastes sweeter: Vietnamese jackfruit tastes sweet and crisp, while Hainan jackfruit tastes light and soft.

2. The price is more affordable: Vietnamese jackfruit is cheap, while Hainan jackfruit is high.

3. High nutritional value: Both of them have rich nutritional value, but Vietnamese jackfruit may be slightly better.

The above is just my personal opinion, and there may be other reasons why Vietnamese jackfruit sells better than Hainan.