When choosing a Content Management system or a shopping cart for your web site it is usually a good idea to ask yourself - what is the problem you are trying to solve?
Choosing the right CMS (Content Management System) is very hard. Most people (as noticed on quite a few message boards) make same mistake - they try to figure out what software they need to make money online. "I want to create a community, what software do I need?". First of all - what kind of community is it going to be? Writers? Photographers? Make-up artists? Everyone has different requirements, and different level of knowledge. Photographers are a little easier to please, as they are used to complicated and cumbersome camera controls, but try to cater same interface to a community of models and make-up artists (same industry, after all) and you will be hit with an outcry for mercy.
Choosing a shopping cart is just one notch easier. First - customers already knows that he wants a shopping cart solution. Second - he is aware that whatever choice he makes is going to affect him in the future. Uploading or entering inventory is a time consuming task and not many people have time to experiment with that. But the ultimate question remains the same - what kind of problem the customer has? What is he/she selling and in which quantities?
There are customers who's only reasonable solution would be an eBay. Some people can use quick shopping cart options, like PayPal's shopping cart or BuyNow buttons, or even CafePress. Some could benefit from ZenCart, osCommerce, VirtueMart or peers. Sometimes company grows out of bunch of Excel spreadsheet and starts using CRM, sales and inventory tracking systems, such as RegKeeper, some flavor of QuickBooks, Configure One's electronic catalog software or other platforms. Certain clients order a custom web site with integrated CMS and shopping cart.
Using full-blown shopping system if you only need to sell two flavors of your widget is unwise. Using PayPal for web store with thousands of clients may cost you significant percentage of your business. Each tool has its own (limited) scope of use. Management 101: Before offering a service think - what is the problem the service is going to solve. If you have the answer to this question - you will find tools in no time.
