In reality, the only real difference is storage space and speed. The SSD will be much faster than the HDD, but at the cost of low storage capacity. There are some claims to power savings with an SSD, but it's a massive debate on whether it's actually true or not, and, to my knowledge, no one has really proved they improve battery life.
I would go with whatever suits you. If you want to be able to do things fast, get the SSD. If you need to store a fair few things on this netbook, get the HDD.