Prestashop is much easier to user and learn, has many premade themes/templates also if you start now and you have a small web store I definitely recommend it. It is user friendly and budget friendly but the scalibality is low (e.g. on a massive scale you will experience big loading times and back-end lagging)
Magento it might be more complex, but it is good for large stores with more visitors. It has very good built-in features,etc,etc. As an Ecommerce it is very complicated even administration needs advanced technical skills and also it can be expensive as you might need programmers and goes on for plugins, changes ,etc,etc