If you take a look at their app section, you will find a bunch of different people creating plugins. Ask yourself, how reliable are these people and will they update their plugins? At least with a hosted shopping cart, you know that a professional company is handling all of that. We got that out of the way and I will probably shake some heads with the above statement.
Keep shaking your heads, facts do that to people . Moving on. Over the past several years developing online stores, I found that there is a short list of reliable shopping carts that are perfect. These carts include BigCommerce, Shopify, Volusion, and 3dcart. They are very similar in terms of features and reliability. However, each has its own ups and downs as does any other product or service.