Here's why I believe SBI! is great for beginners. They really drill in the importance of learning how to plan your site so you create a website that draws in targeted traffic. Many beginners rush into creating a site without understanding how to optimize their web pages so they rank high in Google. SBI! walks you through step by step from beginning to end.
They provide a website building tool for beginners that you can use to build your pages. All you do is pick a design and plug in your text. Your site can be up in a few hours.
The difference in SBI! versus any other ecommerce solution is that they provide the education you need to succeed. You can't just put up an ecommerce site and expect people to just find you. That's not how it works. SBI! helps people find you and teaches you how to write so you convert those visitors into sales.
So many people sign up with Yahoo Store or some other store provider and realize they have no idea how to bring traffic to their store. Suddenly they've wasted their time and money and realize they can't get any sales.
They also have a built-in application called Store Build It! that you can use if you plan on selling products. I've never used it but there's a site you can check out called jugglenow.com. They use Site Build It! and the Store Build It! add-on.
Here's a page that lists all the tools and services you get for SBI!.
http://buildit.sitesell.com/main/tools.html