One of the most important factors when choosing between self hosted and hosted ecommerce platforms like BigCommerce, Shopify and Volusion is to determine weather you would like the the ability to be completely free from the limitations and restrictions imposed by these hosted platforms.
On a hosted ecommerce platform you are not only renting the hosting but you are renting the shopping cart software itself. You do not have access to the source code, so if you would like extensive customizations or for it to function differently, you may able to work around their limitations, but it will be expensive, typically even more so than implementing the same functionality with your own system. This is because a lot of extra work needs to be done in order to inject JavaScript and sometimes implement external functionality and the end result is never ideal, because of the lack of true integration. An additional downside is all of the effort that you put into creating the custom functionality to work with a hosted ecommerce platform will only work with that platform, so you are stuck and if they decide to change the internal functionality of their platform, which they often do, all of that custom work you had implemented may not work anymore.
On the other hand, if a particular hosted ecommerce platform works well enough for your purposes and you don't care to make any significant customizations, then it could be an easy way to get started selling online.
Having your shop online is an investment, we're of the opinion that owning what you pay for is the better investment.